#help-28

1 messages · Page 169 of 1

tough nest
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How?

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im guessing logˇ10 16?

ancient folio
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Pretty useless if u use log base 10

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16 = 4^2

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Use log base 4

tough nest
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no?

ancient folio
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Do u know the basis of log?

tough nest
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Yeah

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kidnda

ancient folio
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Rewrite 16 = 4^2 then

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Whats the whole thing looks like?

tough nest
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Logˇ4 16 = 2

tough nest
ancient folio
#

Whats 0.25 = ?

ancient folio
#

I want u to rewrite the whole thing down but convert 16 to 4^2

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@tough nest Has your question been resolved?

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maiden knot
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I’m confused about how we factor our 1/2 x but then we also have x^1/2 in the denominator?

steel cove
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we factor out a 1/2

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we keep the x^-1/2

rancid acorn
maiden knot
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Oh my god wait lol there’s already an x in front there

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I completely missed it

maiden knot
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pearl trout
pearl trout
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So let's say we have 3Z <= Z

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i.e. integers that are 0 mod 3 form a (normal) subgroup of Z

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So by the above theorem we find that 3Z/3Z <= Z/3Z

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i.e. 3Z/3Z forms a subgroup of Z/3Z

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ah, nevermind.

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void jackal
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void jackal
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hii, is my answer for 17b correct? thanks

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@void jackal Has your question been resolved?

void jackal
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<@&286206848099549185> sorry for tagging

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@void jackal Has your question been resolved?

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@void jackal Has your question been resolved?

void jackal
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<@&286206848099549185> thanks :)

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@void jackal Has your question been resolved?

marble roost
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.close

torn gust
# void jackal

one thing off, since it's qj, that adds to the pj, so they're together in the pythagorean formula

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since it's sqrt(x^2+y^2+z^2) and there's two y vectors to add

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merry olive
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hi

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merry olive
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idk where to start

stiff musk
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which question?

merry olive
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i guess the first one to start but both

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merry olive
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<@&286206848099549185>

torn gust
# merry olive

integrals don't care about coefficients and adding things, so integral of 13f(x)+20 is 13*(integral of x) + (integral of 20), you can separate things

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so you just multiply what they give you by three and add the integral of -5 from 1 to 3

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which is just a rectangle

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the second question is kind of a trap, with exponentials anything added up top is just a number you can pull in front
like e^(x+6)=e^6 * e^x

merry olive
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where did you get the 13 from

torn gust
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just an example

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I used random numbers

merry olive
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oh ok

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what do you mean by multiply what they give me?

torn gust
merry olive
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got it. thank you. could u help me with one more question or should i go into another help room

torn gust
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you can ask here

merry olive
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actually ill ask tomorrow im tired lol

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thanks though

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blazing dome
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blazing dome
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I know what I have to do

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just curious:

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can i integrate the (6-y^2)^2 as a whole quantity and not the stuff inside the parentheses?

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meaning: 6-y^2 as a quantity

boreal stump
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what do you mean

blazing dome
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like as if i just treated the integrand as u^2 - 3^2

boreal stump
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no unless you're integrating wrt 6-y^2

blazing dome
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ok ok

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calm ridge
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How to prove forward direction?

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calm ridge
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Like how do u prove that N(T) = {0v} in general

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do u let some arbitrary x,y in the vector space V

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and then let T(x) = T(y)

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?

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Cuz like backwards, u let T(x) = T(y)

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then T(x) - T(y) = 0w

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and then due to linearity T(x-y) = 0w

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Since N(T) = 0v

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this would imply that x-y = 0v

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so x = y

boreal stump
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if v is some non zero element in N(T) then
T(v+w)=T(w) for any w but then T is not injective

calm ridge
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oh

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so to prove it

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I have to disprove that N(T) can't have any non zero vectors?

boreal stump
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you can disprove that N(T) can have any non zero vectors

calm ridge
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ok

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thank u

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lavish terrace
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lavish terrace
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i dont understand how this converges

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@lavish terrace Has your question been resolved?

calm ridge
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By bct u know that (2^2n + 5^n)/(6^n+2^n) < (2^2n + 5^n)/6^n

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nvm

lavish terrace
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i did a ratio test and got this but the answer is suppose to be converge

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wintry tendon
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midnight field
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hi

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Please don't occupy multiple help channels.

undone vector
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visual mural
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visual mural
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Im solving 2 and

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This is my graph

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How do i know where it intersects with the 2root2 + 1?

craggy tapir
sinful tartan
visual mural
craggy tapir
visual mural
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gotta reach 5000 before graduation

visual mural
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Thays genious

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Thanks

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I get multiple x though

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How do I know which one is the point that intersects?

craggy tapir
craggy tapir
visual mural
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but in the answers

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7pi/2

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9pi/2

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pi/2

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are the ones that intersects

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like what about 3pi/2

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where did that go

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oh is it because

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from 3pi/2

craggy tapir
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seems like your graph is wrong

visual mural
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it becomes negative?

visual mural
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ohhh i figured it our why 7pi/2

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thanks

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agile ermine
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help please

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agile ermine
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no clue what to do

lofty vine
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write the general form of a quadratic

agile ermine
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i did 7 = k(x-2)(x-4)

lofty vine
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$f(x) = ax^2+bx+c$

glossy valveBOT
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Obotron

agile ermine
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oh

lofty vine
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equate f(2) = f(4)

nimble current
lofty vine
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you can find max value by completing the square or sub in the middle point of the parabola

river stream
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0=(x-4)(x-2) 7 is max point

agile ermine
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why tho

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i don't understand it

river stream
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f(x) is basically y

agile ermine
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yeah

river stream
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and x is x

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so when y=0 x=2

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and y=0 x=4

agile ermine
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ohh

river stream
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-> y=(x-4)(x-2)

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and when max point

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m = 0

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y=x^2 -6x + 8

agile ermine
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yeah

river stream
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dy/dx

nimble current
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💀

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???

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you do not need calc

river stream
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i aint using calc

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ik is 2x-6

nimble current
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@agile ermine if a quadratic has zeroes at two values, then its max will occur at their midpoint

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so you can use this fact to solve it pretty quickly

agile ermine
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wdym has 0s

nimble current
nimble current
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in this case, the zeros would be 2 and 4

agile ermine
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ohh

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yeah

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the question states that

river stream
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you need to work out the function first

nimble current
river stream
agile ermine
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pls the quickest way

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or easiest way

nimble current
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yep, that's the way im showing you

river stream
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just do x=3

nimble current
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so we've already shown that f(x) = k(x-2)(x-4)

agile ermine
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yes

nimble current
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so when we plug in 3, we must get 7

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which means you can solve for k

agile ermine
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where did we get the 3 from?

nimble current
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3 is the midpoint of 2 and 4

agile ermine
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oh

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we plug 3 into x?

nimble current
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yes

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we subsitute 3 for x and 7 for f(x)

agile ermine
nimble current
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because we are told that the maximum value is 7 and we've deduced that the maximum value must occur at 3

nimble current
agile ermine
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soo

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then that means

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7 = (3 - 2) ( 3 - 4)

agile ermine
river stream
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you missing k but

agile ermine
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7 = k (3 - 2) (3 - 4)

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and do i expand?

nimble current
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first simplify the 3-2 and 3-4

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and then solve for k as usual

river stream
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k=-7

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so what is k

agile ermine
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k = -7

river stream
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then what is the equation

agile ermine
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-7 (x-2)(x-4)

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do you always use the mid point to sub in x?

river stream
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so that is the function?

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i dont think so

agile ermine
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f(x) = -7(x-2)(x-4)

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then how do you figure out x?

river stream
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but you put the x back into it to check if the answer is correct

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normally a quadratic function is ax^2+bx+c

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if that his way of doing it and is correct i guess i learned something new today

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for now i do my way

agile ermine
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i'm still confused on how the x was found or where it came from

river stream
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i have no idea because i didnt do it this way

agile ermine
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how did you do it?

river stream
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i have no idea where k(x-2)(x-4) came from

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idk what is k

agile ermine
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that is the method given in my book

river stream
agile ermine
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this is an example given in the text

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book

river stream
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the thing is this is a different thing

agile ermine
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so this textbook is cooked

river stream
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the other one was given another one and this is given a max point

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in the k one you were given

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C is 16

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this one you were given the max point + C is 7

agile ermine
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ohh

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so what is the method of solving it?

river stream
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so you have to workout C this time

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y=(x-2)(x-4)

agile ermine
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yeah

river stream
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but C is the number that causes the extra chage

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so Y = (x-2)(x-4)+c

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7=3^2-6(3)+8+c

agile ermine
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how do you know when the method to solve it requires a c value?

river stream
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7=9-18+8+c

agile ermine
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what part of the question clued you on this

river stream
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you werent given a gradient

agile ermine
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the max point is 7 right

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what was the gradient

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oh

river stream
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you dont need the gradient on this

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because is a quadratic which means every single point on the curve have a different gradient

agile ermine
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oh yeah

river stream
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you can workout from the direct f(x)

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and differenciate it

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but for max point

agile ermine
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i might continue this tmr, i have to sleep

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its alr 1am

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thank you for your help tho

river stream
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so you know it is y=mx+c where x=3 and y = 7

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c=8

agile ermine
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this was the answer

river stream
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i did this the wrogn way

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-7 is the gradient

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change in y change in x

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ok i am dumb

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indigo orchid
#

how many five-digit natural numbers can be formed from the numbers 0-9
How many are divisible by five?
I? Numbers are not repeated

indigo orchid
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I need help with this math problem

steel cove
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First one is easy enough

indigo orchid
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I can calc the Number of all, but i dont know about the one divided by 5

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I know

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I got that

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Already

steel cove
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A fifth of all numbers are divisible by 5

indigo orchid
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You mean divide by 5?

steel cove
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?

indigo orchid
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I dont understand rn

steel cove
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Actually wait

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Ok so

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First question

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What did u get

indigo orchid
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27 216

steel cove
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How did u get that

indigo orchid
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10!/5! - 9!/5!

steel cove
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Oh wait

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Oh i mistyped into my calc

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Alr yeah thats right

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So the numbers that are divisible by 5 are those that end in 5 or 0

indigo orchid
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Yy

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I know

steel cove
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Ok

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So you just calculate that

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How many end with 5 or 0

indigo orchid
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Yeah

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How tho

steel cove
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Calculate how many 5 digit numbers are of the form abcd5 and of the form abcd0

indigo orchid
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But its 9!/4!

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No?

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Times 2

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odd rose
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.

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How is this (c)

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low echo
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Hiii

odd rose
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hi, any idea why this is c?

low echo
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I get it probability of choosing cider is 5/8 and beer is 3/8

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Now of 16 students it says x = number of students who get exactly two ciders

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so the prabability of getting exactly two siders for one student is 5/8 * 5/8 * 3/8 * 3c2

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Note it is mentioned all students get exactly 3 drinks

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So now this above value is the success = p of distribution

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Calculate q by using q = 1 - p

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Then find the distribution and expected value of students getting exactly 2 ciders

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There could be a easy way but this is what all i see

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Got it ?

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torn jolt
#

**I am searching for videos related to a particular topic. However, I would prefer more didactic learner sheets instead. **"The concurrency of arbitrary triangles BKB KBK BBB and right-angled triangles."

atomic hare
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are you talking about triangle similarity theorems and special right triangles

atomic hare
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uhhuh

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bok kat bok => side angle side or SAS similarity

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i think youll have more luck looking up the english names instead of polish

torn jolt
#

Form a playlist of videos from you tube related to these topics.

atomic hare
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you want me to... make a playlist for you?

torn jolt
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Yes, by gathering yt videos related to these topics.

atomic hare
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why cant you do it

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i gave you the english names

torn jolt
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Because, Idk how to search this? lol?

torn jolt
#

What do you mean?

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🤔

atomic hare
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i... told you what the english name is

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look those up instead of the polish names

torn jolt
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For the whole topics?

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Check again.

torn jolt
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Thats 1 / 13

torn jolt
atomic hare
#

💀 cant you google the rest

torn jolt
torn jolt
#

Omg..

atomic hare
#

that thing is written in english already

torn jolt
#

Its Ai generated.

atomic hare
#

lMaO

torn jolt
#

Are you helping or twerking?

atomic hare
#

anyways

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you should be able to google the other topics

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i dont see any problems with the terms used there

torn jolt
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Help me or let someone else help. Don't waste my time. BRUH.

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No rude, no help. Good.

lucid flower
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no one else is gonna help you with this sorry, if you want a youtube playlist you gotta make one yourself

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you’re asking someone else to make a google search for you, someone told you how to search it and then you got mad

torn jolt
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I don't want a YT playlist. I want a group of videos. BRUH.

torn jolt
#

Can just the helper talk?

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You have to tell me you can't do it? Just don't answer.

atomic hare
torn jolt
#

Either I am getting old, or I am in the wrong place.

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fking .close

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torn jolt
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torn jolt
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Cna anyone check if my answer is correct

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@torn jolt Has your question been resolved?

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@torn jolt Has your question been resolved?

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river stream
#

@torn jolt i can not really see the question

torn jolt
river stream
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i dont think there can be a constant coefficient @torn jolt

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y=ln(x^2) / x^2y^3+1+x

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wild fox
#

Hi, I have a question about differential equations, when dealing with something like dampened pendulum motion
we have to solve for the differential of $l\frac{d^2\theta}{dt^2}+\frac{d\theta}{dt}b+g(\theta)=0$
which gives $Ae^\frac{-b}{2l}e^{\pm\sqrt{\frac{b^2}{4l^2}-\frac{g}{l}}}$
I have a question about the square root part of the e exponent $e^{\pm\sqrt{\frac{b^2}{4l^2}-\frac{g}{l}}}$
how does this get turned into
$cos(\omega't)$ exacly? ($\omega'$ = $\sqrt\frac{b^2}{4l^2}-\frac{g}{l}$) ?
why does the $\pm$ dissapear? and how is this turned into a complex exponent?

wild fox
#

sorry still learning LaTeX lol

glossy valveBOT
#

Mephisto

torn gust
#

hmm the only way you go from e^ to cos() is with these identities

wild fox
#

oh so the $\pm$ just indicate the two solutions, and then we just take the linear combination by adding them up and deviding by 2?

glossy valveBOT
#

Mephisto

torn gust
#

oh yea e^(positive)+e^(negative) means cosine, that's good

wild fox
#

and I assume that the $\frac{A}{2}$ part of the equation just gets absorbed into the constant?

glossy valveBOT
#

Mephisto

wild fox
#

but where do the i's come from though? I have e to a real exponent

torn gust
#

yea the Ae^(real number) part just stays in front

#

maybe b^2/4l^2-g/l is a negative number so it becomes imaginary

wild fox
#

ohh so we factor -1 out?

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$e^{\pm\sqrt{(-1)*(\frac{-b^2}{4l^2}+\frac{g}{l})}}$

torn gust
#

yea with the b and g terms flipped

glossy valveBOT
#

Mephisto

torn gust
#

assuming that makes physical sense

#

then you do the 1/2 part and replace it with cosine of the inside

wild fox
#

yeah b is generally smaller then gravity

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alrighttt this makes alot of sense now

#

thank you!

torn gust
#

np 👍

wild fox
#

one more question, when solving for the amplitude after a time t, why does the cos part dissapear? let's say we want to know what the damping factor b is, if we reach 50% of our intial angle, after 5min/ 300sec?

#

so if we would plug everything in, the cos part of the equation would just give $cos(\omega'300)$

glossy valveBOT
#

Mephisto

wild fox
#

but it become 1 for some reason, why?

torn gust
#

amplitude is like the top of the wave

#

and cos() is just a thing waving between -1 and 1

#

so if you plug in cos=1 you get the curve above the wave

wild fox
#

oh so we assume that cos(omegat) is 1, because 50% of the amplitude is reached after 5minutes?

#

so it has to be at its 'highest' amplitude possible at that time

torn gust
#

yea here's the picture

#

you just care when the red part hits half A0

wild fox
#

ohhh ok

#

so when amplitude is ever mentioned, or calculating when amplitude becomes x, the cos part is assumed to be 1 or -1

torn gust
#

yes

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it's like ignore the wiggle

wild fox
#

yeah, it's like a discrete function of amplitudes

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alright thanks alot again

torn gust
#

np

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fast marlin
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fast marlin
#

Wouldn’t you add p(b)*p(a|b)?

tribal viper
#

Y

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Don’t u use multiplicative principle thing

fast marlin
#

Because that’s a different event that could occur if b happens first then a could happen given b

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Then that’s still p(a and b)

quartz gale
#

I’m sure there is some intuitive understanding of this equation

#

But this equality is how you define p(a|b) so you can’t change this definition by adding p(b)*p(b|a)

neat aspen
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wintry birch
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wintry birch
#

I shall show that this mighty thing is a well defined, open, not empty interval in R. I get the task somewhat, but i always struggle to get behind the "well defined" stuff. What do i have to show to proof that its "well defined"? i dont want a solution, rather just the thing that i need to show.

neat aspen
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!original

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Please show the original problem, exactly as it was stated to you, with the entire original context. A picture or screenshot is best. If the original problem is not in English, then post it anyway! The additional context might still be helpful. Do your best to provide a translation.

wintry birch
#

"Let A be open in R with standard metric" was missing

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The rest is exactly what i said 🙂

neat aspen
#

basically you need to consider when there's more than one representitive (u,v) which a belongs to

wintry birch
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Mhhm, but what couldnt be well defined then? i mean then just both (u, v)'s would be in Ja.

neat aspen
#

well that's your job to consider, in this particular example you're asked to show it's well defined so these Ja's will have only one interpretation

#

i can give you an example of something not well defined if you'd like

wintry birch
#

Yeah, maybe that helps, cuz i dont seem to understand the problem.

neat aspen
#

ok so let X, Y be sets

#

and define the function $f(c) = 0, c \in X$ and $f(c) = 1, c\in Y$

glossy valveBOT
#

chebyshev's infinite pee norm

neat aspen
#

what happens when X and Y are not disjoint?

#

then they're going to contain a common element, say d

wintry birch
#

okay, i do see the problem here

neat aspen
#

what should f map d to?

wintry birch
#

yeah, thats understandable.

#

🙂 Buut....

neat aspen
#

your (u,v)'s are not disjoint

#

for example

#

$J_0 = \bigcup {(u,v)\mid 0\in(u,v)\subset A}$

glossy valveBOT
#

chebyshev's infinite pee norm

neat aspen
#

well 0 can be chosen from the representative $(-1, 1)\cap A$ as well as the representative $(-2, -2)\cap A$

glossy valveBOT
#

chebyshev's infinite pee norm

neat aspen
#

it's your job to show that $J_0$ can be uniquely defined regardless of the representatives 0 is coming from

glossy valveBOT
#

chebyshev's infinite pee norm

neat aspen
#

and in particular all $a\in A$

glossy valveBOT
#

chebyshev's infinite pee norm

wintry birch
#

Im sorry, im feeling very dumb, but what does the representative has to do with it? I thought that Ja is just the combination of all of those representatives. Why even should one be choosen that zero comes from?

neat aspen
#

i was just giving a particular example $J_0$ but you need to show it holds for all of $a\in A$

glossy valveBOT
#

chebyshev's infinite pee norm

wintry birch
#

Yeah, but still. Ja includes every representative. Why should one be prioritised if i throw everything into one pot?

neat aspen
#

but it's a generalised union

#

you need to show that this generalised union is a unique representation

#

it can't be the case that J_a = one thing = some other thing that's different

wintry birch
#

Okay, but what aside from "The union of all the intervals of A that include a" should it be? blobcry I hate this stuff, proofing something is well defined was always the hardest part for me. Even some rather simple exampels like the modulo addition or smth like that. Bc here i have one, imo clear definition. Why should i get something different when i use other representatives if i just throw in every interval?

neat aspen
#

well it's based off the metric/topology right

wintry birch
#

i guess

neat aspen
#

Why should i get something different when i use other representatives if i just throw in every interval?
well you shouldn't in this particular question because it is well defined, you're just tasked in arguing it

#

i think you may be over thinking it

#

its likely exactly what your intuition is telling you

#

if a is a member of two representitives, then a should also be in their union

wintry birch
#

Mhhhm...

neat aspen
#

so if we take a in J_a it shouldn't matter which representative (u,v) a is coming from

#

when we consider the open sets J_a

wintry birch
#

Ahhh, is my task to show that: if a in (r1, r2) and (r3, r4), then J_a ist the same whether we first do (r1,r2) u (r3,r4) and then put it in J_a or just put them both in J_a?

neat aspen
#

pretty much yeah

#

i assume you're trying to show J_a is a topology?

#

er

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satisfies the topology axiom

wintry birch
#

The task wants to show that A is always a union of disjoint intervals

#

Can i ask you a quick follow up question on that task? its on my proof that its really only one interval for every a.

neat aspen
#

do you mean J_a is just one interval for every a?

wintry birch
#

yeah

#

im not sure if my argument is perfectly fine

#

I did the following:

If A=R, its trivial
If A!=R, and a in A, w/out loss of g, there ex. an x in R\A s.t. x>a -> M={x in R\A | x>a} has a lower bound and therefore must have an infimum. -> (a-E, inf(M)) is completly in A and open. But for every b<a, x>inf(M), there must exist a point in X\A s.t. its an element of (b,x), therefore (b,x) is definitely not in A.
-> J_a has the supremum inf(M).
same argument for lower bound. Every for every point p in between J_a's supremum and infimum, its either p=a, which is in a, or its p<a, then we take (inf(J_a),a) or its p>a (a, sup(J_a)). therfore J_a = (inf(J_a), sup(J_a))

neat aspen
#

A is just a connected open set no?

wintry birch
neat aspen
#

oh not connected sorry

#

what is your set X

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(a-epsilon, infM) ?

wintry birch
#

Oh, its just R lol

neat aspen
#

o

wintry birch
#

i always switch them up, cause in the uni we always talk about X, not R specifically

neat aspen
#

ok i think i am brain lagging

#

But for every b<a, x>inf(M), there must exist a point in R\A s.t. its an element of (b,x), therefore (b,x) is definitely not in A.
-> J_a has the supremum inf(M).

#

why does this imply J_a has the supremum inf(M)

wintry birch
#

Wait, i wrote it a little unclear.
Consider b>inf(M). For b to be in Ja, there must exist an interval (l, u) s.t. l<a, b<u completely in A. But bc b>inf(M), there must exists at least one x in R\A in (inf(M), b), otherwise b would be a greater lower bound for M. --> x in R\A c (inf(M), b) c (l, u) -> (l, u) !c A. Therefore b cannot be in Ja.
-> inf(M) is an upper bound for Ja.

#

and bc every a<x<inf(M) is in A (otherwise inf(M) wouldnt be a lower bound for R\A), this means that inf(M) is the smallest upper bound for Ja, thus the supremum

neat aspen
#

ok yea

#

Every for every point p in between J_a's supremum and infimum, its either p=a, which is in a, or its p<a, then we take (inf(J_a),a) or its p>a (a, sup(J_a)). therfore J_a = (inf(J_a), sup(J_a))
what are you doing here exactly?

wintry birch
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Im sleepy, its again wrong, i would have to use an Epsilon with the a somehow. But its just there to show once again that for every x in between those two bounds, we really find and intervall, which is rather dumb, cause i could just give the interval (inf(Ja), sup(Ja)), i was freestyling and hadnt exactly thought it through

neat aspen
#

lmao ok

#

i haven't thought too hard but maybe try showing (sup -M, inf M) and J_a are subsets of each other

#

and once you have that

#

to show well defined, take a = b, and show that J_a = J_b

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wild fox
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Hi, I don't really understand divergence of a vector field and its implications
So by definition a divergence of 0 implies no sinks or sources
does that mean that the vector field has no attractor? or does it mean that the vector field never converges?
Should I interpret it as vector field density?

wild fox
#

can it be interpreted as instantenious change of direction?

#

as in if you would take the corss product of a vector at F(x,y,z) and F(x+dx,y+dy,z+dz), and took the divergence of it, it should give zero?

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viral jasper
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Divergence, in short, is the instantaneous measure of how much a field is going into, or out of a specific point

#

Zero divergence means that the field is flowing into a point at the exact rate as it is flowing out

wild fox
viral jasper
#

Yes exactly

#

Check out the definition at Wikipedia

https://en.m.wikipedia.org/wiki/Divergence

In vector calculus, divergence is a vector operator that operates on a vector field, producing a scalar field giving the quantity of the vector field's source at each point. More technically, the divergence represents the volume density of the outward flux of a vector field from an infinitesimal volume around a given point.
As an example, consid...

#

Divergence is defined as the limit of the flux as the enclosing volume approaches zero

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scarlet iris
#

how did he get the W to be [1,0]?

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scarlet iris
#

isnt the w supposed to be a transpose of one of the rows of the (A-lambda*identity) vector?

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dreamy torrent
#

I need help with part b. I know that there is only 1 way when the first number is 4, but idk how to model the number of ways for numbers 3,2,1

torn gust
dreamy torrent
torn gust
#

yup, so just do that and remember you can't use 0

dreamy torrent
torn gust
#

yea it's choosing

#

same reason why sets are written increasing order {1,2,3}

dreamy torrent
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ok

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thanks

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slender heart
#

What formulas would I use for each of these

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slender heart
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celest pewter
#

should be $P' = P(1 + \frac{r}{n})^{nt}$ for all of the ones where you compound every period of time

if there's no period you can just do $P' = P \cdot r^t$

glossy valveBOT
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simple mica
#

just need help with c

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simple mica
#

help c?

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the answer key shows 24

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but idk how to get that number

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<@&286206848099549185>

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tropic torrent
#

This is more compsci than stricly math but I need to make a parser for propositional logic using bnfc so if anyone's familiar with that tool, could you take a look at where my mistake is.

These are the contents of my bnfc file for prop logic.

AtS. S ::= Ident ;
NegS. S ::= N ;
ConjS. S ::= C ;
DisjS. S ::= D ;
ImpS. S ::= I ;
EqS. S ::= E ;

Neg. N ::= "(" "-" S ")" ;
Conj. C ::= "(" S "&" S ")" ;
Disj. D ::= "(" S "|" S ")" ;
Imp. I ::= "(" S "=>" S ")" ;
Eq. E ::= "(" S "<=>" S ")" ;

From this definition:

Definition 
The sentences of propositional logic language L based on the non-empty set of atomic sentences P are formed as follows: 
1. Every atomic sentence p∈P is a sentence of the language L. 
2. If α and β are sentences, then (¬α), (α∨β), (α∧β), (α→β), (α↔β) are also sentences of language L. 
3. Only strings formed on the basis of the two previous rules are sentences of the language L. 

Example 
If P={p,q} , then for example p,q,(¬p),((¬p)∨q) and (((¬p)∨q)→p) are sentences of language L, but not (¬()) nor (p∨r).

Automatic grader gives me 0 points but no feedback as to why lol. I have a little over 100 tests of my own that the resulting parser passes.

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distant silo
#

I had this exercise on an exam today, so I decided to check it with symbolab, but I can't seem to get why it gets a different answer from mine. Could somebody explain? it somehow gets a second -1 in the final solution and ends up with -2/9, I solved it several times and can't seem to find out how. It does solve it in a different way(with substitution), so it's possible it got it wrong but it's more likely that I got something wrong somewhere and can't find out what...

distant silo
#

It's a fairly simple integral too 🤔

stiff musk
#

cos(0) is 1, not 0

distant silo
#

.

#

oops

stiff musk
#

mystery solved ⚔️

analog raptor
#

blud was doing meth and math at the same time

distant silo
#

Im so stoopid 🤦‍♂️ well thx

stiff musk
analog raptor
#

relatable

stiff musk
distant silo
#

!solved

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.solved

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stiff musk
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quick sage
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dreamy torrent
#

how do u guys do part a without the integration (it's 1 mark)?

modern oracle
#

1/2a is const

dreamy torrent
#

oh is the graph just a rectangle then?

modern oracle
#

yes

dreamy torrent
#

doesn't this equal 1

#

but the answer is 2a

glossy valveBOT
modern oracle
#

if you have same probability to choose x from a and 3a

dreamy torrent
#

yes

dreamy torrent
modern oracle
#

yes

dreamy torrent
#

ok thanks

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ashen laurel
#

.reopen

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.open

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livid scarab
ashen laurel
#

Ik i gotta do that i need help after that part

#

😭

#

Its giving me an answers that are wrong when i do it

crisp fossil
#

what answers are you getting

ashen laurel
#

I got x^2-x once

#

💀

crisp fossil
#

yeah i know how

#

you plugged in x-1 instead of (x-1)

ashen laurel
#

I also got x^2-2-1

#

😭

crisp fossil
#

try replacing the x's in the first equation with (x-1)

ashen laurel
#

🤧🤧

crisp fossil
#

dyk how parentheses work in math

ashen laurel
#

Im dumb af when it comes to math ugh

#

😭

crisp fossil
#

nah you probably arent

ashen laurel
#

Working on it 😔

crisp fossil
#

anyways try this
(x-1)^2
vs
x-1^2

#

what is the difference?

ashen laurel
#

Well in the first part its being squared with the whole bracket while in the second its being squared with -1 only

crisp fossil
#

yeah so when you are replacing the x's in the function, you have the replace the x with the whole thing and make it parentheses

#

so the first answer would be:

(x-1)^2 - (x-1)

ashen laurel
#

Yeah i got to that part

#

We put down the formula there right?

crisp fossil
#

which formula

ashen laurel
#

(a-b)^2

crisp fossil
#

well i wouldnt really think of that as a formula right now

#

if they make you expand this then FOIL out the first term

ashen laurel
#

🤔

crisp fossil
#

and then distribute the negative in the second term

ashen laurel
#

Foil? 😭

crisp fossil
#

basically x^2 is x*x correct?

ashen laurel
crisp fossil
#

(x-1)^2 is gonna be (x-1)(x-1)

ashen laurel
#

Ahhh

crisp fossil
#

so you can multiply those two together to make
x^2-2x+1

ashen laurel
#

Is that the final answer?

crisp fossil
#

no

#

thats the expansion of the first term

ashen laurel
#

🤔

#

Uhuh

crisp fossil
#

(x^2-2x+1)-(x-1)

#

solve that and thats your answer

#

what do you think it is

ashen laurel
#

x^2-3x+2?

crisp fossil
#

correct

ashen laurel
#

Ah

#

😭😭

#

And the second part??

crisp fossil
#

do the same method

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rough walrus
#

i know i need to show work but i honestly don’t know what to do here

quartz scroll
#

6444

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lunar fiber
#

Think I missed something in class, how am I supposed to solve this?

lunar fiber
#

I mean I could definitely solve it but it would take a decent bit of calculating and I don't think that's the proper solution

torn jolt
#

wait nvm

#

if you look at the OBC triangle

#

is it a right angle triangle?

lunar fiber
#

I can't really tell

torn jolt
#

I don't think I can assume that since there is nothing that claims it is

lunar fiber
#

Yeah

#

It might be though, lemme solve it assuming it is rq

#

I have the answer so that may be the case and the question is just stupid

torn jolt
#

I think it should be stated if it was, since then the OB side would just be the radius.

#

There might be some formula for this though lemme check.

lunar fiber
#

Yeah it isn't a right triangle

torn jolt
#

You might be able to set up a system of equations using this, but no idea if it is the right solution.

lunar fiber
#

Maybe? I'm not completely sure how to do that though

torn jolt
#

is the solution radius = 18 cm?

lunar fiber
#

Should be 10cm

#

Unless I wrote the wrong number

torn jolt
#

yeah then that formula didn't work.

lunar fiber
#

Was sleeping during class and I just copied down what I thought was the answer

torn jolt
#

Mark the foot of O on the chord AB

#

and connect it

#

this would be a perpendicular bisector

lunar fiber
#

Then what?

torn jolt
#

let the foot be D

#

then

#

AD would be 13/2

#

following?

lunar fiber
#

Yep

torn jolt
#

CD would be 13/2 - 4

lunar fiber
#

5/2

#

I got about that far earlier but didn't know what next

torn jolt
#

yes now you can find OD

#

since ODC is right angled at D

#

Now consider the triangle ODB

lunar fiber
#

No idea how I didn't figure that out earlier lol

torn jolt
#

you can now find OB which the radius

lunar fiber
#

I think I get it

#

Thanks 🙏🏻

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torn jolt
#

is this right

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torn jolt
#

and this

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balmy flicker
#
  1. Daniel often watches two of his satellite channels on TV. He knows that Kanal A shows 18
    minutes of advertising per hour and Kanal B shows 13 minutes of advertising per hour. He also knows that the two channels show commercials at times that are not dependent on each other.
    a) Daniel turns on channel B. What is the probability that the channel is showing advertising at that moment?
    b) Daniel hits his TV on another occasion. What is the probability that
    at least one of the two channels Kanal A and Kanal B is showing something other than commercials at that time?
balmy flicker
#

I need help with B

nimble current
#

what is the complement of the probability you want to find?

torn jolt
#

is the answer for (a) 13/60 ?

nimble current
#

yes

torn jolt
#

thank you

#

(b) would be P(A)+P(B)+P(A)*P(B)

#

right?

#

@nimble current

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balmy flicker
#

The procentage

#

Of the B

#

answer on a) is 22%

balmy flicker
#

a is 13/60

#

aka 22%

#

b) answer is 93.5 %

#

I just need explaintion on how

nimble current
#

so you can use complementary probability @balmy flicker

nimble current
#

the probability that at least one of the channels is not showing comericals is 1 minus the probability that both channels are showing comericials

balmy flicker
#

exactly

nimble current
#

the latter probability is 13/60 * 18/60 = 0.065 = 6.5%, so the answer is 100%-6.5%=93.5%

balmy flicker
#

🤦‍♂️

#

I am so stupid

#

thanks for the help

#

I read the question wrong

#

I did 47/60 X 42/60

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torn jolt
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torn jolt
#

#14

umbral dome
#

what about it?

torn jolt
#

Does the dimension of H equal the dimension of the basis of column A

#

And why

umbral dome
#

what is H?

torn jolt
#

H is a subspace

umbral dome
#

in this question we are considering the subspace which is the span of the 5 vectors given

torn jolt
#

Do I need to use the basis theorem
I barely understand it

umbral dome
#

since we put them as columns of a matrix, it is also by definition the column space of the matrix

torn jolt
umbral dome
#

so we have that the column pace is span{c1, c2, c3, c4, c5} (where c denotes the columns). so by definition the set {c1, c2, c3, c4, c5} spans the space

#

however, they are not linearly independent, so they are not a basis.

#

We are trying to find a subset of {c1, c2, c3, c4, c5} that has the same span, and which is linearly independent

torn jolt
#

So c1 and c2 form the basis because they are pívot columns

#

OHHHH I GUESS SO

umbral dome
#

yes. they span the same space: span{c1, c2, c3, c4, c5} = span{c1, c2}, and they are linearly independent

torn jolt
#

the rest are just linear combinations of the first two!

#

OHHHH

#

omg

#

It’s making sense

#

because like a basis generates all the points in the subspace???

#

and these two vectors generate everything else

umbral dome
#

yes. the original 5 columns did that too, but they were redundant (we didn't need all of them). so a basis is the set of vectors that does that without any redundancy (the bare minimum needed to generate the subspace)

torn jolt
#

Yesssss

#

I saw that in one YouTube video

#

What about rank A + dim Nul A = n

#

So if I wanted dim Nul A

#

Is it 3

umbral dome
#

yes

torn jolt
#

and I saw in a yt video
This guy said n is like a steak
The meat is the rank and the dim Nul A is the fat

umbral dome
#

the null space of A is the set of solutions to Ax = 0, and each "free column" (non-pivot column) contributes a parameter/free variable

torn jolt
#

Right! That’s why we put Ax = 0 in parametric vector form, because we putting free variables in terms of basic variables

#

NO

#

Basic in terms of free

#

Yeah

umbral dome
#

yes, so then we write the solution as [ t_1 \vb{v}_1 + t_2 \vb{v}_2 + t_3 \vb{v}_3 ] which is exactly the same as $\nullsp A = \vspan{ \vb{v}_1, \vb{v}_2, \vb{v}_3}$ (so the nullspace is 3-dimensional)

glossy valveBOT
#

pnoןɔ

torn jolt
#

I’m stressed I have an exam tomorrow 😭

#

Yeah

#

How about 15

#

How do I do it

#

There can only be 3 pivot positions

umbral dome
#

so if there are 5 columns and 3 pivots, what is the dimension of the column space, and what is the dimension of the null space?

torn jolt
#

Dim H = 3

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steep dragon
#

I’m assuming I use the fact that a matrix is invertible iff det neq 0

#

it definitely won’t be diagonal as I will have a number and -a^2 in the first col

neat aspen
#

you could use column 5 as the coefficients for cofactor

#

it's all 0 except the last entry

#

then keep cofactoring with the maximum amount of 0's

steep dragon
#

would it be beneficial to row reduce first, or at any step because there’s a lot of nonzero terms

#

with the first submatrix because we get rid of the a in the first column, we can get rid of all of the entries in that column

neat aspen
#

haven't gone through it myself but if you see any point that you can row reduce for more 0's then it's probably recommended to do so

#

since it will save you alot of computation time

steep dragon
#

alright thank you

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violet loom
#

how would I go about this integration., i cannot work out how to sub u into this

neat aspen
#

looks like to rewrite x in terms of u and then differentiate

violet loom
#

differentiate?

neat aspen
#

so that you can substitute it in

violet loom
#

hold up ill try that thanks and get back to you!

#

like this?

neat aspen
#

hmm

#

looks ugly

#

lemme think

violet loom
#

but how would i get rid of the 1/(x+9x^3)

#

like wait ill show

neat aspen
#

well x = 1/sqrt(9(u - 1))

violet loom
#

is that legal

neat aspen
#

but it looks ugly so i am doubting this approach

violet loom
#

lol that would be so clapped but yeah that could work but would it really be easy to integrate

neat aspen
violet loom
#

is that a does not equals sign

neat aspen
#

yea

violet loom
#

ahhh

#

i even asked chat gpt still couldn’t do it

neat aspen
#

oh

#

it's partial fractions

#

i think

#

how did i overlook that

violet loom
#

how would i do partial fractions sorry

neat aspen
#

oh have you not learned that yet

violet loom
#

no maybe its assumed knowledge i must have forgotten

neat aspen
#

it's just if you have a denominator as a product of polynomials, you can rewrite it as a sum that looks like this

#

$\frac{r(x)}{p(x)q(x)} = \frac{a(x)}{p(x)} + \frac{b(x)}{q(x)}$

glossy valveBOT
#

chebyshev's infinite pee norm

violet loom
#

oh ok i see

#

how could that be applied here tho

neat aspen
#

have you seen this before?

violet loom
#

yea

neat aspen
#

you have $\frac{1}{x(1 + 9x^2)} = \frac{something}{x} + \frac{something else}{1 + 9x^2}$

glossy valveBOT
#

chebyshev's infinite pee norm

violet loom
#

ahh

#

yeah

#

but what is something and something else

neat aspen
#

if you're familiar with the process of partial fractions, then it'll be your job to figure out what those somethings are

violet loom
#

ye okay

neat aspen
#

That's not what the partial fractions should be

#

how did you get thos

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steep dragon
#

it isn’t when they’re both 1 because we could have i=1 and k=0 and a fine derivative

#

wait when they’re both zero i+k=0 so can I just have the sun from zero to d?

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steep dragon
#

<@&286206848099549185>

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steep dragon
#

<@&286206848099549185>

steep dragon
#

bruh someone please 😭

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empty plover
#

I have a quick question. How do I solve this?

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lavish stag
#

How would I do this? I'm not 100% sure how do to find the coordinates for the graph when i am just given the derivatives and intervals.

royal grotto
#

I can give a rough idea

Start by marking the given points, then use all of the other information to understand how the funciton behaves between those points

f'(x)=0 signifies that the slope of the graph at that point is 0 in other words the normal at that point would be horizontal
f'(x)>0 means that the function is increasing in that interval
and vice versa for f'(x)<0

f''(x)=0 means that that point is the point of inflection
f''(x)>0 means that the graph has upward concavity in that interval
and vice versa for f''(x)<0

lavish stag
#

okay, I'll try and let you know how i do!

royal grotto
#

sure, gl!

lavish stag
# royal grotto sure, gl!

I'm still a little confused on the analyzing the derivative part, How do i determine where the function is increasing or decreasing based on the derivatives?

royal grotto
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lavish stag
#

this lowkey still does not make sense to me 😭 🙏

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dense edge
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dense edge
#

did I solve this correctly? does it want a matrix for the answer or x and y value as the answer?

quartz gale
#

There is a problem here

#

Did you calculate at any point AB ? Or BA ? @dense edge

dense edge
#

Just did that now

quartz gale
#

Okay so you agree that what you did was wrong ?

dense edge
#

yeah im not sure what i found

#

A+B

#

what i need is AB

quartz gale
#

It’s just that you just solved A=B

dense edge
#

oh ok

quartz gale
#

Look at the first photo

quartz gale
quartz gale
dense edge
#

is this getting any closer lol

#

i found y now

quartz gale
#

Too bad

#

Almost everything is good

#

Except the first thing you calculate for BA

#

look at the first coefficient you calculated

dense edge
#

i dont see it

quartz gale