#precalculus

1 messages · Page 280 of 1

vestal zenith
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but did your teacher teach you how to make a regression?

viscid thistle
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no

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I have no idea what to do

vestal zenith
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I can show you how to do it on wordmat

viscid thistle
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ok

vestal zenith
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first you make a table like the one in the picture

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and then you choose the wordmat tab > regression > exponential regression

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and you get the following equation

viscid thistle
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huh

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Hm

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Do you know how to do it on a graphing calculator?

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I have to find the a and b values though

vestal zenith
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yes you can see the a and b values in the equation

viscid thistle
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I need a graph though

obsidian monolithBOT
viscid thistle
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ok

vestal zenith
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you can plug the equation in your graphing calculator

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but I can see in your case the form is:

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$y=a \cdot b^x$

obsidian monolithBOT
vestal zenith
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so what's the value of a and b here? @viscid thistle

viscid thistle
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I don't even know so confusing

vestal zenith
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look at the picture I sent

viscid thistle
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Can you show me it on paper @vestal zenith over text is hard

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Ye

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Idk how you got those numbers though

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in the progress

vestal zenith
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it's a bit hard to explain when you're not used to wordmat

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and i'm wondering why your teacher haven't taught you how to do regression yet

viscid thistle
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ok ty

thin jewel
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anyone help me with velocity problem?

vague hearth
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Y = ab^x where a is the initial value and b is the growth factor

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Or decay

trail niche
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Depends

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If x>1 it’s growth

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If x<1 it’s decay

rare zephyr
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is there such thing as the inverse of a factorial

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like how division is the inverse of multiply

prime yoke
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can someone simply explain the reasoning behind why floor(-x) and -floor(x) are different

undone pawn
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n < x < n+1
=> floor(x) = n

-(n+1) < -x < -n
=> floor(-x) = -(n+1)

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@prime yoke

supple hazel
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yo im so lost right now

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#33

thorn agate
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Can anyone help me with a d solve it.

late pewter
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which part are you stuck on

mystic umbra
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@thorn agate

thorn agate
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I dont know how to do it man.

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If you could brief out the steps.

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Will be helpful

late pewter
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have you learned about derivatives?

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if not have you learned anything about exponential growth

thorn agate
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Yes

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?

late pewter
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rate of growth

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thats just a derivative

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sapphire grows overtime at a declining rate

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thats also a derivative

late pewter
hexed granite
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if anyone knows any lmk

hexed granite
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I need 7, or 8

lunar axle
proud raven
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do you have any notes?

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this is usually what youll use for C -> P

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obviously youll need to simplify

clever pecan
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r means radius

viscid thistle
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yes.

crude pilot
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yeah

astral knoll
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yes, as it has changed cot into 1/cot which is wrong.

viscid thistle
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Would the quadratic function be A(x) = 6^2 + 12x + c?

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not even sure

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@astral knoll

astral knoll
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Area=width * length, so new area is (6+x)(12+2x), now multiply and u will get the result in the form asked.

viscid thistle
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for a question like this

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are we supposed to assume that the right triangles evenly share the height of the pole

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so like each side thats adjacent to the pole is 15 ft

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or am i getting that wrong

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bruh

viscid thistle
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@astral knoll Would it be (x+6) and (2x+12)

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How you factor?

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512=2x^2+24x+72

crude pilot
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divide it by 2 then factor

trail niche
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Since they got different angles

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Try treating the whole system as one big triangle by adding the two angles

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You know the height of the base

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And the angle of one side

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Crap actually nvm then u can’t use trig

worldly radish
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ping me 🙏

steel tulip
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What have you tried so far?

worldly radish
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well im just wondering what am i supposed to do with A, B, and C

potent imp
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plug in -2 into the equation

worldly radish
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-1 if x<0
-1 if x is greater/equal to 0

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soo the 1st part is true but the 2nd part isnt

potent imp
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yeah, because -2<0

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so the first rule applies

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so its 3(-2)+5=-1

worldly radish
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and that would be the answer for a?

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and youd do the same for the rest?

potent imp
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yeah

worldly radish
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what about this part here

astral mantle
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what part of this are you confused about?

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if x=3 then h(3) = 6

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otherwise, just substitute x into the other equation

potent imp
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also note that the other equation simplifies to x+3 if x is not 3

quartz oxide
viscid thistle
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@quartz oxide do u still need help?

quartz oxide
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yea

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@viscid thistle

viscid thistle
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ok, do you remember solving quadratic equations during Algebra II?

quartz oxide
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yea kinda

viscid thistle
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okay great, so simplify this let's just refer to this as $3x^2 - 7x + 2 = 0$

obsidian monolithBOT
viscid thistle
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do you know how to put the equation into factored form?

quartz oxide
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would it be (3x-1)(x-2)=0

viscid thistle
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yep

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so now we can put sin back in there, and we get $(3sin(x)-1)(sin(x)-2)=0$

obsidian monolithBOT
viscid thistle
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we can set each equation equal to zero, getting the equations $3sin(x)-1=0$ and $sin(x)-2=0$

obsidian monolithBOT
quartz oxide
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so is that the solutions for [0,2pi]?

viscid thistle
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Well, you can simplify it and find an exact value by solving for $sin(x)$. first equation would be $sin(x)=1/3$ and the second $sin(x)=2$

obsidian monolithBOT
quartz oxide
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ohh ok

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thanks man

thorn lily
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I need to solve for x (the original problem is circled). Below the problem is my work so far, but I’m stuck on how to get the x’s on one side of the equation. My teacher wants us to provide the exact solution and an approximate solution.

shrewd root
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last step not so right

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we have to "move" all the x to one side

thorn lily
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Ok, what did I do incorrectly? And how do I move the x to one side?

shrewd root
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u have to expand the brackets when it first appears

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then move all x term to one side by addition/subtraction

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then factor out the x

thorn lily
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sorry, how do I expand the parentheses?

shrewd root
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(x-1)log2: x log2-log2

thorn lily
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Ok, I understand that part, thank you.

shrewd root
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yes!

thorn lily
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Thank you!

shrewd root
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but not done yet

thorn lily
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Yeah. Where do I go from here?

shrewd root
thorn lily
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By factor it out do you mean divide?

shrewd root
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2x + 4, factor out 2 becomes 2(x+4)

thorn lily
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Ah ok

shrewd root
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factor means take out common factor

thorn lily
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Thank you so much for the help!

shrewd root
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looks good

sinful gull
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What do you mean..

onyx gazelle
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Never mind I figured out my own question

sinful gull
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Alright then

iron pendant
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can someone help me with this?

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<@&286206848099549185>

trail sun
agile owl
sick steppe
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polynomial of degree n will have nth differences be constant @agile owl

agile owl
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im not sure what that means

sick steppe
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Lines (degree 1 polynomials) have constant 1st difference
quadratics (degree 2) have 2nd differences constant
etc

agile owl
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oh ok then that's degree 4 cuz its x^4?

sick steppe
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yes

agile owl
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that makes sense thank u

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the word differences messes me up

sick steppe
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yes

worldly radish
agile owl
sick steppe
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d = an! @agile owl

agile owl
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d=4(3!) ???

sick steppe
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yes

agile owl
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oh

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omg i learn this in class and these r so confusing

elfin arrow
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Can anyone help me solve this question? "A balloon drops 2 balls with a time of 3s between the drops, after 10 seconds the first ball reaches the ground, how high is the balloon? (tag me if u can help me out)

serene river
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anyone?

ember socket
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Hello

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I am Solving a exponential function. I’m at 4^2x+9=12

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So after subtracting nine on both sides I end up with 4^2x=3

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What would be the next step ?

main narwhal
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you would take log, base 4, on both sides

ember socket
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So log each side ?

main narwhal
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yup

ember socket
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Ok thanks a lot I was stumped on that and was unsure on what to do

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Logs are so confusing

main narwhal
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the rules may take some getting used to

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but it is fine more exercises or examples will treat it as 2nd nature

ember socket
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Indeed I’m still getting used to them after a week of practice

main narwhal
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perfectly normal take some breaks in between overwork will prevent you to have the "aha" moment

oak skiff
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hey can anyone help me? i just cant rember how to go about this

main narwhal
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Do you know what is sec x equal to?

cobalt swallow
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@oak skiff you need to use this arcsinu + arccosu = pi/2

serene river
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yo

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??

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this should be zero triangles

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right

shrewd root
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infinite, question is not well defined

viscid thistle
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hm

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wouldnt that be ambiguous case

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then you use law of sines to figure out the sides and angles*

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you can determine whether it’s obtuse or acute right after

drowsy karma
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How do I do this?

misty imp
viscid thistle
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@misty imp try symbolab

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it’ll show you steps

misty imp
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it says i have to pay for steps :c

viscid thistle
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hm

misty imp
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it gives answer but idk rly how to do it myself

viscid thistle
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lets see, uk how they give you steps but its incomplete

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you could open it on another tab and put that part where it was incomplete

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then it shows you the steps on how to complete it

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@misty imp

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I had that trouble back then too

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lol

misty imp
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ooh okay ill try

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thank u :0

viscid thistle
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ye, plus no one’s rlly around here
kinda depressing

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@misty imp did it work

misty imp
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yeaa it kinda worked but it has fractions for exponents

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my teacher said no fractions

viscid thistle
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ic

misty imp
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didnt rly pay attention in class so idrk how to fix it

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eek

drowsy karma
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Pls help

smoky pagoda
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x + 3y = 12 and 3xy is as big as it can be. First thing to note is both numbers have to be positive : if only one is negative so will the product, but if both are negative the sum cannot be 12. Next to try and find y you might want to consider all multiples of 3 smaller than 12 and compare against a necessary x value. Compare these products and take the maximum (this is assuming the question wants integer answers)

drowsy karma
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Okay thanks

scarlet oak
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@misty imp check out the laws of logarithms. For this problem in particular pay attention to the product rule and quotient rule

vapid mica
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i got 9.13

brazen tundra
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i found the angle measure using inverse tan but what do i do after to find the weight?

shrewd root
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i think u have to resolve the force/tension in the diagonal cable to balance out the horizontal force and vertical mass

brazen tundra
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how exactly do i do that?

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<@&286206848099549185>

agile owl
vestal zenith
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you can plot the function in your graph calculator and check it

agile owl
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ok

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what does it mean by negative?

viscid thistle
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That's not even close to the method they probably want them to approach this

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@agile owl consider how can you express that a number is negative first

agile owl
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what? like -1?

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is it like xER and yER?

sick steppe
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f(x) < 0 means f is negative

agile owl
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ok i get that

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i think it's (-inf, 1) and (2,3)

sick steppe
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yes

viscid thistle
agile owl
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-infty?

oak skiff
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anyone free to vc to help me with 2 problems?

bitter sandal
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hey, how do i find the root of a non-factorable cubic equation?

the equation is: P(x) = 5x³+21x - 2

uncut mulch
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that's not a cubic

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its a quadratic in which case you could use the QF

bitter sandal
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its 5x³ sorry

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the whole equation is: 5x³ + 14x + 7x - 2

uncut mulch
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the presence of 14x and 7x separated like that is very suss

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are you sure its not supposed to be 14x**^2**?

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because that would have nice roots

bitter sandal
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nopee its 14x + 7x

uncut mulch
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typo in the question?

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,w solve 5x³ + 14x^2 + 7x - 2 = 0

bitter sandal
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prolly, but its still solvable right?

obsidian monolithBOT
uncut mulch
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,w solve 5x³ + 14x + 7x - 2 = 0

obsidian monolithBOT
bitter sandal
uncut mulch
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solveable yes, but very ugly

bitter sandal
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i think i'd go with 14x²

uncut mulch
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use cubic formula and/or depressed cubic

bitter sandal
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yeah it looks ugly

bitter sandal
uncut mulch
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fancy name related to what i stated

bitter sandal
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oh..

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lmaoo

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but thanks

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:)

pale python
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when finding non-permissible values of a rational expression, only the numbers on the denonminator is what you're working with, right?

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Yes

uncut mulch
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for rational expressions, the numerator would be defined everywhere so yes you only need to consider the denominator when determining non-permissible values

pale python
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Alright, thanks!

bitter sandal
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how do I find the polynomial equation using the quotient and remainder?

uncut mulch
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its better if you post the whole question

bitter sandal
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okay, uh, "Write a polynomial division that has a quotient of x+5 and a remainder of -2"

uncut mulch
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consider the quotient-remainder form:
P(x) = (x-a)Q(x) + R(x)

bitter sandal
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ahh that one! thank you

scarlet oak
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Hey all, is there a reason to use cardans method to solve cubic equations? Im using the "a0/an" method that I've seen which is easier. If it's worth the time, I'll learn the cardan method

cobalt swallow
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well use whatever can be used to solve, there is no set method. Studying Cardano's method is useful nonetheless, because sometimes the usual techniques don't work , it is a method to find the real roots of general cubic equation so sometimes does come handy, it is kinda like the quadratic formula method.

scarlet oak
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Does cardano's method always work?

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Also, do cubic equations come up in calc 1 or 2?

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I was having trouble finding a video to explain cardano's method; most of them are in hindi, and I've yet to learn how to speak it

cobalt swallow
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I think this is enough, just write cardano's method , and a load of stuff is on internet in english

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@scarlet oak

scarlet oak
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Thanks! I'll definitely check it out. @cobalt swallow

tribal vapor
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given a recursive sequence definition

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lets say you want to find like the 4th term

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is there a way to find just that one term, without having to start from the first term and progressing until you reach the 4th?

fringe quartz
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ye there is a way

tribal vapor
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how

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for example

fringe quartz
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well

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should be obvious that

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every term is you just adding +3

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to the number

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so you want 4th term. just multiply the 3 by 3

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add 9 to 15

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you get 24

tribal vapor
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thanks

fringe quartz
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which term you want

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4?

tribal vapor
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yeah

fringe quartz
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yes

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if you are not sure you can check 1 by 1

tribal vapor
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yeah i just verified it with some python

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do you know what the recursive definition for this sequence would be?

gaunt mason
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Hmmm, there might be many.
If you assume the form of
a_n + A a_n+1 + B a_n-2 = 0

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Inputting exact figures, give you 2 equation of 2 variables, A and B.

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@tribal vapor

tribal vapor
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Can you elaborate on that formula

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What's it called, I've never seen it before

gaunt mason
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It's a classical recursive formula with 3 terms

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You can have more or less terms, but this is like the most common one.

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You can have for example
a_n + A* a_n-1 = 0

inner iron
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i need some help

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with these radian trig equations

inner iron
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Solve the trigonometric equation for all values −3π≤x≤3π. 2sin1/3x-sqroot3=0

desert axle
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hi I'm in elementary school how do I start learning calculus now I want to make my paretns proud

amber laurel
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any knows what this means?

uncut mulch
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expressing something in base $\red{a}$ would mean to express it in the form ${\red{a}}^b$

obsidian monolithBOT
amber laurel
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so for b for example its 2^64^2-x?

past meadow
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no

clever pecan
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@past meadow why so?

past meadow
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Because 2^64^2-x doesnt equal 64^(2-x)

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And its also probably not even what they meant to write

clever pecan
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I'm assuming you let 64^(2 - x) = 2^a, and solve for a in terms of x

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for problem (b)

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same for problem (a)

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but just 3^a

clever pecan
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nobody has spoken in this channel since?

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lol

quick kelp
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I guess...

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I'm stuck with a question

quick kelp
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suppose the graph of y=ax^2+bx+c has its highest point at (1,7) and it's y-intercept is -3. Then what is a, b, and c?

viscid thistle
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@quick kelp are you still stuck?

quick kelp
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yes sirr

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do you have to use a two point slope?

viscid thistle
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Consider what happens at the y-intercept

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ie what's the x value that characterises it

quick kelp
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mhmm

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isn't the y-intercept the same as the value of c?

viscid thistle
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Ok yeah ig you could think it that way

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If you are in the form y=ax²+bx+c yes, as when the function hits the y-intercept, x is 0, so you'd notice that y=a(0)²+b(0)+c simplifies to y=c

quick kelp
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ohh

viscid thistle
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Then what's our c?

quick kelp
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the y-interceptt

viscid thistle
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I mean what's the value of the constant c

quick kelp
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y?

viscid thistle
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You are given the y-intercept, aren't you?

quick kelp
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yes

viscid thistle
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If you know the y-intercept, and we just established that c represents the y-intercept, what's our c

quick kelp
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mhmm

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-3

viscid thistle
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Good job

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Now we have y=ax²+bx-3

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Ok next piece of info

quick kelp
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ohh!

viscid thistle
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What can you do with the info: "highest point at (1,7)"

quick kelp
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you can plug it in

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?

viscid thistle
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Yes

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And you get an eqn

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Our goal is to make a system of 2 eqn's to solve for a and b

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What's the other equation you can have

quick kelp
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hm..

viscid thistle
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Think about highest point

quick kelp
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(h,k)

viscid thistle
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Think about what does that mean

quick kelp
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vertex?

viscid thistle
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Yeah

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And what are the characteristics of a vertex

quick kelp
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it has a vertex form?

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is that the other equeation?

viscid thistle
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Do you know how to get the vertex if you have for example y=x²+x+1

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This is just an example

quick kelp
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do you use an equation form?

viscid thistle
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I want to see if you are able to do it numerically

viscid thistle
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Uh i really have to go, i'll be back in some time

quick kelp
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oh it's alright

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You really helped

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I can go n from what you said

viscid thistle
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Ok gl

quick kelp
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you made it much clearer

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thank you!

viscid thistle
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I'll be here after if you still don't get it

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Yw!

fiery wave
#

@quick kelp if it can help, recall that the x coordinate of a vertex (in the form ax^2 + bx + c) is -b/2a

quick kelp
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yes

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hmm

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so..

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-7/2(1) if i am not wrong?

fiery wave
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No, you don't have a and b yet

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You have x = -b/2a
You are given x. What is it?

quick kelp
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is x

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1?

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correct me if i am wrong:(

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if i am right

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would it be

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1=-b/2a?

viscid thistle
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Yes.

quick kelp
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okay

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so far

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the only i got is for c which is -3

quick kelp
fiery wave
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Because now you have 2 equations

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The one you got by plugging (1,7) into the rule

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And the one you just got

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You can find a and b that way

quick kelp
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hm...

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let me think this through

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i'm so sorry I don't know how to continue

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so I got 2 equations which is 1=-b/2a and

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y=ax^2+bx-3

fiery wave
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You're close

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Plug (1,7) into y=ax^2 + bx - 3

quick kelp
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7=a(1)^2+b(1)-3?

fiery wave
#

Yes

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So 7 = a + b - 3

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You now have two equations involving a and b. Can you solve?

quick kelp
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Ohhh

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okok im solving it rn

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what I did

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I got the value of a from 7=a+b-3

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which yield to a=-b+10

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then plugged the the value of that a to 1=-b/2a

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and got a b=20

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and used that value of b again to 1=-b+10

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so i got a=-10 b=10 c=-3

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b=20*

fiery wave
#

Looks good @quick kelp

quick kelp
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Oh my god

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thank you so much

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thank you to both of u! Really appreciate the help!

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And the time you gave for a stranger :))

iron pendant
harsh smelt
#

@iron pendant are you familiar with unit circle?

uncut mulch
#

describe what you did

lunar axle
viscid thistle
#

Is this a test?

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@lunar axle

lunar axle
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no it’s homework

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@viscid thistle

blissful ridge
#

Looks correct

lapis bone
#

hi pls help

fossil crownBOT
#
Rule 4

If your question has not been answered for a minimum of 15 minutes, you may use the Helpers tag once. Please do not try to bump your question using this ping unnecessarily. Do not abuse this ping. Do not individually ping users with the Helpers tag without their express permission.

bleak torrent
#

I'm stuck at d

stuck lark
#

we can do some algebra then recognize a derivative

bleak torrent
#

I have no clue what that means

stuck lark
#

$\frac{1-2\cos(x)}{\pi-3x}=\frac23\frac{\cos(x)-\frac12}{x-\frac\pi3}$

obsidian monolithBOT
bleak torrent
#

Ohhhhh

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Thxxx uu

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I got it

stuck lark
#

you're welcome

bleak torrent
#

Idk if it's right or not

cobalt swallow
#

it is not that the answer is wrong but the way you did it, firstly you seem to have used the fact lim x-> 0 sinx/ x =1, nothing wrong with that , but your second step is wrong, in the way that it does not lead to third step the way you did it , to get to the third , you don't do multplication in sin, rather you do it outside sin, and that you will multiply by (m+n)(m-n)/4 , both above and below ( I repeat outside of sin) , then you will get the third step as you have

#

@bleak torrent

#

and after that you use lim x-> 0 sinx/ x =1 , so the third step expression will directly be as k^2 will cancelled when you use that fact , so -2 (m+n)(m-n) /4 =
-(m+n)(m-n)/2 the answer you got ,

bleak torrent
#

I see

#

Thank u

prisma glacier
#

Hey! I'd like to simplify sqrt(16+sqrt(31))-sqrt(16-sqrt(31)) into sqrt(2) but I don't know how to proceed! Does someone have an idea? Thanks!

uncut mulch
#

you could try assigning a variable to your original expression,
square it in an attempt to simplify some of the square roots and see what happens

bold knoll
#

hi hi. quick question.
i came across this identity in my book, is there a name for it?
$a_0=0, {\sum_{i=1}^{n}{(a_i -a_{i-1})}} = a_n$

obsidian monolithBOT
viscid thistle
#

telescopic sequence

#

in a sense that a lot of terms vanish

odd shell
#

Hi, I'm a little confused on how to do this type of question:

#

The point (1, -2) is on the graph of f(x). Describe the following transformations on f(x), and determine the resulting point:

#

g(x)=2f(x)+3

sick steppe
#

@odd shell do you have the transformations from f that make g?

odd shell
#

@sick steppe yeah that is why i am confused

#

this is the only information that is given to me

sick steppe
#

ok so what does the 2 do? and what does the +3 do?

odd shell
#

well so the 2 would be a vertical strech? and the three a vertical translation up?

sick steppe
#

yep

#

vertical stretch by a factor of 2, vertical translation 3 up

#

Now determining the resulting point means you want to know g(1)

but g(1) = 2f(1) + 3, but f(1)=-2

odd shell
#

so then would it be g(1)=2(-2)+3

sick steppe
#

yes

odd shell
#

g(1)=-1

#

like that?

#

ok ty

sick steppe
#

yes

bleak torrent
bold meadow
#

0/0 so L'Hopital's rule

uncut mulch
#

consider 1 = sin(pi/2)
and the limit definition of the derivative

fathom phoenix
bold meadow
#

a. 1st derivative

viscid thistle
#

use derivativees @fathom phoenix

#

or

#

use $x = \frac{-b}{2a}$

obsidian monolithBOT
fathom phoenix
#

ok thanks

bold meadow
#

ax^2+bx+c
c determines the height, changing this doesn't change the maximum height?

viscid thistle
#

it doesn't change where the maximum height is

#

$x = \frac{-b}{2a}$ is where the maximum is

obsidian monolithBOT
viscid thistle
#

according to a quadratic in the form $ax^2 + bx + c$

obsidian monolithBOT
viscid thistle
#

changing $c$ changes the max value, it just doesn't change where it is (along the x-axis)

obsidian monolithBOT
viscid thistle
#

If you want to solve for maximum height, you need to do:

$a(\frac{-b}{2a})^2 + b\frac{-b}{2a} + c$

obsidian monolithBOT
viscid thistle
#

where you plug in $\frac{-b}{2a}$ for $x$

obsidian monolithBOT
fathom phoenix
#

oh wow lol i didnt even think of this

#

ill go back and check

#

thanks again

blissful gale
sour plinth
#

use the arithmetic series formula $\frac{n}{2}(2a+(n-1)d)$

obsidian monolithBOT
blissful gale
#

how do i do the sum 165 part

sour plinth
#

let it equal to 165

#

then you know the values of a and d

#

a=5 and d=2

#

so solve for n

blissful gale
#

i put =165 at the end?

#

do the ns cancel out

sour plinth
#

no

#

solve for n

#

$\frac{n}{2}(2(5)+2(n-1))=165$

obsidian monolithBOT
blissful gale
#

bro how

sick steppe
#

it's 1 eqn 1 unknown

bright grail
#

i tried finding the inverse but i got stuck trying to isolate

signal pivot
#

So the input of ln can't be negetive or zero i.e it has to > 0

\begin{align*}
e^{x^2-x}> 1\
\therefore \hspace{6pt} x^2-x>0\
\end{align*}
So that gives either x=0 or x=1

obsidian monolithBOT
bright grail
#

how did you go from e^x^2-x > 0 to the second one

#

removing the e

#

and how did it go from > 1 to > 0 @signal pivot

#

i dont understand how to jump to that step

sick steppe
#

e^0=1 @bright grail

woeful fable
#

Is there a reason why during addition identities and subtractions for trig functions, when you break up the inner values, it has to be from the lower value to the greater value?

sick steppe
#

@woeful fable specific example if possible?

woeful fable
#

cos(2pi/12+3pi/12) != cos(3pi/12+2pi/12)

sick steppe
#

They equal the same thing

#

addition is commuative

woeful fable
#

I did the angle formula

#

and they don't equal the same unless I have an algebraic error

sick steppe
#

You likely applied the identity wrong then

#

cos(A+B) = cosAcosB-sinAsinB

woeful fable
#

I did cos(pi/4+pi/6)
Which sums just
cos(pi/4)cos(pi/6) - sin(pi/4)sin(pi/6)

sick steppe
#

yeah

woeful fable
#

That's equal to (sqrt2/2)(1/2) - (sqrt2/2)(sqrt3/2)

#

then that's sqrt2/4 - sqrt6/4)

#

which is sqrt 2 - sqrt 6 / 4

sick steppe
#

brackets

woeful fable
#

wdym

sick steppe
#

(sqrt2-sqrt6)/4

woeful fable
#

I just distributed and simplified

#

yes

#

yea

#

And that's not equal to what it's supposed to be

#

if I did cos(pi/6+pi/4)

#

The top one is my result

#

the correct answer is the bottom one

sick steppe
#

You either added or removed a negative somewhere then

woeful fable
#

cos(pi/4) = sqrt2/2
cos(pi/6) = 1/2
sin(pi/4) = sqrt2/2
sin(pi/6) = sqrt3/2

#

angle addition formula for cos(x+y) is cos(x)cos(y)-sin(x)sin(y)

#

idk where im screwing up

sick steppe
#

pi/6 trig values are backwards

#

,calc cos(pi/6)

obsidian monolithBOT
#

Result:

0.86602540378444
sick steppe
#

,calc sin(pi/6)

obsidian monolithBOT
#

Result:

0.5
woeful fable
#

oh

#

lmao

#

ty

bleak torrent
#

I'm struggling at E

bold meadow
#

0/0 so L'Hopital's

mystic umbra
#

@bold meadow I am trying to work this out on my own but I am not understanding the step by step for e

bold meadow
#

well after using L'Hopitals' you can see that it just becomes:
$\lim_{x \to a} \frac{\sec^2{x}}{-\sin{x}} = - \csc{a}. \sec^2{a}$

obsidian monolithBOT
mystic umbra
#

@bold meadow in my book it says f'/g'

#

so I need the derivitive of (tanx-tana) as step 1 to find f'

#

derivitive wrt x

#

but there is an a there

blissful ridge
#

Divide numerator and denominator by (x-a) and you'll notice that each term becomes the definition of derivative at x=a

mystic umbra
#

ok that matches the book

#

probably harder for me because I forgot the definition of a derivitive

#

isn't that just the definition of the limit of the tangent line?

#

slope of the tangent line

blissful ridge
#

$f'(a)=\lim_{x \to a} \frac{f(x)-f(a)}{x-a}$

obsidian monolithBOT
mystic umbra
#

ok thx

autumn marsh
uncut mulch
#

the solutions aren't pretty

autumn marsh
#

Yeah I saw it on the graph but don’t know how to solve it

#

I mean the results

uncut mulch
#

W-Lambert or something

#

its not really a pre-calc question

autumn marsh
#

Ohhh

#

I don’t understand that method the W-Lambert

cobalt swallow
#

there is 2 solutions only , that can be seen for -2e^(-x) = x-4 by "hand " drawing the graph

#

but yes finding them won't be easy

#

using W lambert is a good way to solve it

autumn marsh
#

Can you show me how?

cobalt swallow
#

it gives solutions W( ...)+ .. something, they are expressed in terms of the Lambert's function , but we need numerical values I don't think you need it, considering you asked it in precalculus

#

I don't know how to do it properly as well

#

Only looked it up when Ramonov told about it, really interesting.

#

many find approximate solutions through iteration

#

maybe using Newton's method

autumn marsh
#

Hmm... I’ll try using Newton’s method

mystic umbra
#

blackpenredpen on youtube does the W-lambert functions method

bright grail
astral mantle
#

do it 5head way by using lhopital

#

cos(0)/1 = 1

viscid thistle
#

geometrical inequality

viscid thistle
viscid thistle
green kernel
viscid thistle
#

why does taking reciprocals flip inequality signs?

#

oh nvm

#

ok tyty

winged cloak
#

Idk where to put this...

#

Do you know how to simplify this?

viscid thistle
#

Have you tried anything so far? @winged cloak

winged cloak
#

@viscid thistle Nvm i did it it was dumb 🤦‍♀️ i just couldn't see it

worn violet
#

Can someone help me with: Graph the function f(x) = cos (x) and g(x)= 1/2 cps (2x-pi) ?

viscid thistle
#

What do you know about the graph of y=cos(x)

worn violet
#

Suppose you need to find the height of a tall building. Standing 20 meters from the base of the building, you aim a laser pointer at the closest part of the top of the building. You measure that the laser pointer is 4◦ tilted from pointing straight up. The laser pointer is held 2 meters above the ground. How tall is the building?

wispy aurora
#

Draw a diagram

worn violet
#

and

echo wagon
#

Show your diagram

wispy aurora
#

^

echo wagon
#

If your diagram is right, it's just a trig question

wispy aurora
#

Yup

#

A calculator related one tbf

#

But trig nonetheless

worn violet
#

can u help me with the diagram im confused

wispy aurora
#

Sure

#

What have you gotten so far?

worn violet
#

not much im generally confused about this

wispy aurora
#

ok, my recommendation is imagining it in your head. Imagine a building, and you walk 20 meters away from it. Now draw one line as the building, and the other line as the path you took 20 meters away from it

worn violet
#

ok

#

now?

wispy aurora
#

Got it so far? Now I recommend drawing a line from the point where you currently are to a point 2 meters above it. That is to simulate the laser pointer

worn violet
#

ok

wispy aurora
#

Now draw a line connecting the laser pointer to the building

echo wagon
#

And show your drawing, even if it's not done and you need help to continue

worn violet
#

yeah im not getting it

#

i need to see it

#

nvm

viscid thistle
#

i think you were the one i was helping who i asked for the diagram but you didn't post it

echo wagon
#

Maybe their phone is too old to take pictures and they're embarrassed to tell us

#

Don't be, only the mods here are elitist. The rest of us are nice.

worn violet
#

no no

#

i solved it

#

lmao

worn violet
#

I just need help with

#

Graph the function f (x) = cos (x) and g (x) = 1/2 cos (2x-pi)

viscid thistle
#

i also said "what do you know about y=cos(x)" previously answering this q and you ignored it or i skipped it

worn violet
#

i apologize i must have missed it

#

@viscid thistle im not sure about it

echo wagon
#

You've never heard of cos before and know nothing about it?

worn violet
#

im talking about the problem

#

i know cos

echo wagon
#

Do you know its graph?

worn violet
#

No I don’t know how to graph it

#

Would it be 2 different functions or one?

echo wagon
#

f(x) and g(x) are two different functions

worn violet
#

So therefore 2 different graphs?

echo wagon
#

You need to know how to graph cos(x), and then apply transformations to it to graph 1/2 cos(2x-π)

#

... Yes

worn violet
#

Ok so like this?

echo wagon
#

Yes, I don't have a lot of time to help. Hopefully someone else can

#

Glad you can send pics now, that will help

worn violet
#

Haha

#

I know you don’t have enough time to help but would that be correct?

viscid thistle
#

if that's supposed to be the graph of y=cos(x), then sure that's fine

#

though it seems you took a pic from desmos

worn violet
#

Yes that’s the easiest way

#

Now I just need to graph g(x)?

echo wagon
#

...

viscid thistle
#

know your transformations

#

as said

echo wagon
#

So you just wanted help on how to enter it into desmos?

worn violet
#

Yes and No

viscid thistle
#

huh

worn violet
#

Because I’m not sure if there’s supposed to be on one graph or two different graphs

#

So now I just to graph g(x) on a separate graph right?

viscid thistle
#

..yes

#

why are you asking me if you are typing letters into desmos correctly?

wispy aurora
#

OOOOF

viscid thistle
#

Me who still hasn’t figured out mobile desmos

viscid thistle
proud sparrow
#

@viscid thistle stop crossposting

viscid thistle
#

Suppose your making a bioweapon that kills 1/3 of the population.

But you & your secret organization of 9 people decide to immunise prior.

If people realize that 1/3 of the population didn't die they'll know you have the vaccine.

How do you change the kill rate to ensure the 1/3 of the population still die even after 10 have been immunised?

#

Supposing the population has 90 people, in normal circumstances 30 people would die.

But you want to change that so 30/81 people will die.

So the formula is like (population*ratio)/(population - vaccinated people)?

#

Does this check out?

proud sparrow
#

@viscid thistle not sure what you are asking... oh, you want to change it to kill 30/81 of the people? looks reasonable...

viscid thistle
#

yea so it doesnt look suspcious when 9 of the 90 people in the population are secretly immunised

viscid thistle
#

I know that logs aren't defined for negative numbers
but is there any other reason as well we can't do this:
ln(1)=0
ln(-1.-1)=0
ln(-1)+ln(-1)=0
2ln(-1)=0
ln(-1)=0

let ln(x)=c, x<0 and c belongs to R
e^c=x
which is not true for any c belonging to R

trim hemlock
#

well its not that it isnt defined

#

but it isnt defined in the real number set

#

but log of a negative number can also be defined by a complex number

potent imp
#

^

#

using e^ix=cosx+isinx

#

or more generally e^(a+bi)=(e^a)(cosb+isinb)

novel cargo
#

I'm not sure if this the place to ask this

#

is there a precedence rule for factorial and multiplication?

#

$3n!$ is $(3n)!$ or $3(n!)$?

obsidian monolithBOT
tawny nacelle
#

i think its the latter one that is more common

#

factorial takes precedence over multiplication

novel cargo
#

thanks

tawny nacelle
#

np catthumbsup

novel cargo
#

checked in Mathematica

#

they give factorial precedence as you said

tawny nacelle
#

nice

serene heath
#

you thought they were lying? smh

tawny nacelle
harsh smelt
viscid thistle
#

!n! what ! comes first?

jagged glade
#

The exclamation mark

tawny nacelle
#

if u do it on both sides, it cancels out

viscid thistle
#

smh !n is subfactorial

blissful ridge
#

Whoa never knew that

maiden pelican
#

How

#

How do you solve this system of equations

#

Parameters are p, q, r and unknowns are a, b, c

smoky pagoda
#

What's troubling you with this system?

#

It can be solved by any standard methods for solving linear equations

#

Gaussian elimination will work just fine here for example

rain notch
#

How would you go about solving #13, just for sine (without calculator).

rain notch
#

<@&286206848099549185> sorry it's already been some time

bold meadow
#

$\sin{-115}=\sin{-25}=-\sin(25)$

obsidian monolithBOT
rain notch
#

Thank you. However, I need to obtain a ratio as an answer, so how would that be done. My teacher had not gone over this type of scenario, where the reference angles are not common like 30, 45, 60, or 90 degrees.

uncut mulch
#

-sin(25°) is exactly what they want

rain notch
#

Alright

#

There is no way to go passed that I assume

uncut mulch
#

the less special angles are 15°, 36°, 72°,75°

rain notch
#

I see

uncut mulch
#

i mean if you read the question, they want
stuff in terms of trig functions of the reference angle

#

so even IF you reference angle would be 30°,
you'd give an answer like -sin(30°) instead of -1/2

rain notch
#

oh alright

#

thanks, I was completely overthinking it

maiden pelican
cobalt swallow
#

@maiden pelican , just solve it the plain elimination way, Using equation (1) and (3), cancel out p, getting an equation in q and r, which you can solve using eqn(2). Doing by gaussian elimination is really quick

maiden pelican
#

Yeah.. I can't do this for some reason, something is going wrong and I don't understand what..

#

Oh I'll do that

viscid thistle
rain notch
viscid thistle
#

Oh I see

echo wagon
#

@mighty talon Bruh, did you join just to spam your dumb competitions in every channel daily?

viscid thistle
#

Doing @ Moderators might be worthy here

echo wagon
#

Idk how they could have missed it

peak badge
#

I will do it for you.

<@&268886789983436800> - can we deal with an ad user here?

odd shell
#

how would you determine the function given this table of values?

#

im stuck someone please help

royal siren
#

infinite

sick steppe
median moss
#

Would someone explain the concept of an infinite geometric series quickly please? Specifically its difference of finite geometric series?

green kernel
#

infinite geometric series go on forever, they have infinitely many terms

#

finite geometric series stop at some point, they have finitely many terms

#

does that answer your question? @median moss

median moss
#

I understand that part, I guess I should be more specific. I don't really get the divergence and convergence part. What role does the common ratio (r) play a part in the sum doesn't really click for me, even though its written there

green kernel
#

well, imagine trying to calculate that sum 1 + 2 + 4 + 8 + ...

#

by hand

#

it will just get bigger and bigger

median moss
#

yep

green kernel
#

it basically goes off to infinity

#

but when you have a sum like

#

1 + 1/2 + 1/4 + 1/8 + ...

#

since the terms are getting smaller and smaller

#

the more you calculate, the slower it will ‘grow’

#

so it will approach some specific value

royal siren
green kernel
#

the terms r^a get smaller and smaller when you have the ratio between the terms is less than 1

median moss
#

Ahh I kinda get that, and it depends all depends on the common ratio I guess

green kernel
#

anything multiplied by a number less than 1 will be smaller

median moss
#

Give me like 10 minutes to just sit on it and try to actually understand and come back to you :)

#

Thanks so much

green kernel
#

anything multiplied by a number greater than one will be bigger

#

so in order for the terms to get smaller and smaller, you need to be multiplying by something less than one each time

#

ie r < 1

#

(at least for positives :p)

median moss
#

Ah got it, and because they get smaller term by term. The sum of these terms will just converge to a sum

royal siren
#

not because they get smaller term by term @median moss

#

it's due to the properties of geometric series - "how fast they get small"

#

for instance, 1 + 1/2 + 1/3 + ... gets smaller

#

but doesn't converge

green kernel
#

yeah, it’s quite subtle. for all geometric series, ‘they get smaller’ is a good enough intuition, but in general you can have a sum whos terms do not get small fast enough for it to converge

median moss
#

I'm probably using the terms converges and diverges loosely as its a calculus term and i haven't done limits yet. So sorry about that

green kernel
#

no dont worry, i just glossed over some details in my explanation

odd shell
#

@sick steppe yea the third differences are constant

#

but what after that?

#

i know that one of the factors is (x-2)

#

but thats it

sick steppe
#

d=an!
constant difference = (leading co-efficient) (degree)!

#

so you know a(x-2)f(x)

odd shell
#

so a would be -1 right

#

what next

sick steppe
#

I guess just use the points and try and find f(x) @odd shell

blissful niche
#

Functions nice!

delicate minnow
#

Anybody here willing to teach me factoring tomorrow?

proud sparrow
#

integer factoring or polynomial factoring?

green kernel
#

teach me how to factor integers in polynomial time

proud sparrow
green kernel
#

isnt that poly time

#

well, better than poly time

proud sparrow
#

not the number of bits

green kernel
#

oh right

delicate minnow
proud sparrow
#

oh no polynomial factoring

#

In mathematics and computer algebra, factorization of polynomials or polynomial factorization expresses a polynomial with coefficients in a given field or in the integers as the product of irreducible factors with coefficients in the same domain. Polynomial factorization is one of the fundamental components of computer algebra systems.
The firs...

proud sparrow
# delicate minnow Poly

do you have a class of polynomials you want to learn how to factor, or do you want to learn how to factor polynomials in general?

#

whoa LLL is crazy

open vortex
#

this might be something really obvious but how would I work out y - 1 as a function of x? Would this be written as f(x) = y - 1?
If it is, then I'm really lost. X is the inputs right, but the x's aren't being mapped to anything so how would there be a solution?

echo wagon
#

Do you have an exact question you are looking at?

open vortex
#

yep

#

The original question was find an expression for the function whose graph is the bottom half of the parabola x + (y -1)^2 = 0.
The hint was can you solve the equation for y - 1 as a function of x?

I'm a bit confused about the hint. (Also I wasn't tooo sure where to ask this as I'm starting calculus at uni but these were meant to be prerequisites)

echo wagon
#

@open vortex Oh, I see

#

Still here

#

,w plot x + (y-1)^2 = 0

obsidian monolithBOT
echo wagon
#

Ping me if you come back

open vortex
#

@echo wagon i'm here

echo wagon
#

Okay, so you just have to isolate y in the equation

#

Make y the subject

#

So what do you think the first thing you have to do is?

open vortex
#

for the hint? How would I make y the subject if its currently f(x) = y -1, would that not be y = y -1

#

for the equation in the original question, i could rearrange and make y the subject

#

actually, i think i tried that but i got stuck at y^2 - 2y = -x -1 when I tried to make y the subject for the original equation

echo wagon
#

No

#

The equation is x + (y-1)^2 = 0

#

Isolate y in this equation

#

Oh, okay, you did do that

#

Didn't read all of it

#

What's the first step?

open vortex
#

ahhh i think i get it! So (y-1)^2 = -x , then square root the -x and add 1?

#

but can we square root the -x?

echo wagon
#

Yes

#

Why not?

#

x+(y-1)^2 = 0 doesn't have solutions where x is positive, so x <=0 and -x >= 0. So you are only taking the square root of nonnegative numbers

open vortex
#

what if x is positive, then we would be square rooting a negative number no?

#

ahhh

#

that makes so much sense!! Thank you so muchh!!

echo wagon
#

But you're not done yet

open vortex
#

im not?

echo wagon
#

What are the solutions to x^2 = 4?

open vortex
#

plus and minus 2

echo wagon
#

Right, so when you take the square root, ordinarily you should do +- in front

open vortex
#

ok so i have 1 +- sqrt(-x) ?

echo wagon
#

But y = +-sqrt(-x) + 1, isn't a function because it gives you TWO values of y for one value of x.

open vortex
#

ahhh i seee

echo wagon
#

Whereas a function should have one and only one value of y for each value of x

open vortex
#

so just -

echo wagon
#

Yeah

#

And if they said the top half of the graph, it would be +

open vortex
#

ahh, got it! Thank youuu :)))

echo wagon
#

Np

astral reef
#

U knw wut this server is friggin boring im leaving

paper zenith
#

ok bro have fun

drowsy karma
#

I wasn't paying attention for one second

astral mantle
#

the pink goes with two consecutive even whole numbers

#

adding two to a whole even number gives a whole even number

drowsy karma
#

well so does 4

viscid thistle
#

if a function is a set of ordered pairs no two of which have the same first member, how are two to one functions functions?

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wouldnt the first member be the domain?

sick steppe
drowsy karma
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am confusion @sick steppe

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wym consecutive

sick steppe
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consecutive means right after each other

drowsy karma
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Ohhh

sick steppe
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so 1 and 2 are consecutive numbers, but 1 and 3 arent

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The question states consecutive even numbers

drowsy karma
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i get it

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so it has to be 2

sick steppe
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so if we assume x is even, the next even number is x+2

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since even numbers occur every other

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you can also think of it as 2n and 2(n+1) for an integer n

robust nest
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We just started these today and all I can do is draw the first part (12 nautical miles)

robust nest
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anyone?

sick steppe
mystic umbra
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this is vector addition

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@robust nest 12 mi is the hypotenuse of a triangle

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N60W is the angle of theta with respect to the y axis

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,w 12e^(i*(5pi/6))

obsidian monolithBOT
mystic umbra
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see the decimal expansion is actually your x and y values

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drop the i

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if you do this twice you will have (x1,y1) and (x2,y2)

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then if you do (x1+x2,y1+y2) which is the sum of the two vectors which is a vector that represents the relative location (final) compared to your starting location

abstract garden
mystic umbra
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,w sqrt(0.688)

obsidian monolithBOT
mystic umbra
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,w sin((236/360)*2pi)

obsidian monolithBOT
mystic umbra
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notice that I use 236/360 to get the % of the rotation

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,w 236/360

obsidian monolithBOT
mystic umbra
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then we want to convert that % to radians

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1 full rotation around a circle = 2pi radians

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so I multiply by 2pi after I do /360 to get the conversion from degrees to radians

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360 deg = 2pi rad

abstract garden
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@mystic umbra how can we get that when we don't have calculator ?

proud sparrow
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in general, you can't

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unless you don't mind whacking by hand

abstract garden
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I see

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Thanks

open vortex
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For this question, why is the answer 3? mostly the f(0) could take any value part

echo wagon
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Well, if f(0) = k then because f is even we get f(-0) = k and there is no contradiction. But if g(0) = k then g(-0) = -k and this only works if k is 0

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@open vortex

open vortex
echo wagon
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Np

viscid thistle
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if a function is a set of ordered pairs no two of which have the same first member, how are two to one functions functions?
wouldnt the first member be the domain? << don't mind the repost im just still confused on it

echo wagon
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@viscid thistle A two to one function just means that there are two different first coordinates that give the same second coordinate

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So the first coordinates are unique, the second coordinates are not

proud sparrow
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{(0, 1) (1, 1)}

viscid thistle
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ohhh for some reason I thought the second coordinates would be unique cause it's one i'm so dumb 😂

mystic umbra
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,w limit x->2 (x^3-8)/(x-2)

obsidian monolithBOT
mystic umbra
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so this can only be done by factoring?

bold meadow
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You can use Lhopital's too

mystic umbra
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actually no

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that is for the derivative right?

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there are times when the limit exists but the derivitive does not exist

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you can have a limit of 0

astral mantle
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lhopitals works because you are dividing by 0

mystic umbra
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but not a limit of l/0

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oh ok

astral mantle
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its 0/0

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when you substitute

mystic umbra
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is hopital's rule for limits or derivitives or both?

astral mantle
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limits of indeterminate form

echo wagon
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Lhopitals is to find limits, by taking derivatives.

mystic umbra
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ok

gloomy swallow
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i need help with dividing polynomials

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is anyonee hereee

harsh smelt
gloomy swallow
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ohh okay

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so

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it is

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x-1/3x^4-6x^2+17x-8

echo wagon
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What do you mean by dividing?

uncut mulch
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$x-\frac13x^4-6x^2+17x-8$?

obsidian monolithBOT
echo wagon
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Because the degree of the numerator is already smaller than that of the denominator

gloomy swallow
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not like tha

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wait a sec

astral mantle
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$\frac{x-1}{3x^4-6x^2+17x-8}$

obsidian monolithBOT
astral mantle
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?

gloomy swallow
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:\frac{3x^4-4x^3-6x^2+17x-8}{x-1}

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$\frac{3x^4-4x^3-6x^2+17x-8}{x-1}

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$\frac{3x^4-4x^3-6x^2+17x-8}{x-1}$