#precalculus
1 messages · Page 189 of 1
could've been simplified more easily without multiplying it out
can you continue from
log_3( 9sqrt(3))
try writing it as a power of 3
3^ 1/2
2
sqrt(3) = 3^ what?
yeh,
9sqrt(3) = 3^(5/2)
yep !
getting better.
needs more practice
yeah
6sqrt(2) = 3 * 2 sqrt (2)
how would I prove the existence of an inverse implies a function is injective
and the other way
$\forall b \in B: \exists ! a\in A: fa=b \Leftrightarrow \exists f^{-1}: B \to A$.
mop:
sorry mental blank
$\exists g : B \to A: g \circ f = i_A \wedge f \circ g = i_B \implies \forall b \in B: \exists! a\in A: fa=b$ is ez
mop:
because if the composition of f and g is injective, f and g are injections
could anyone give me a hint about the other way
<@&286206848099549185> has been > 15 mins since q was posted
Hi guys, I'm having a lot of trouble verifying this problem. I'm trying to get one side to match the other. I've tried turning tangents on the left side into sin/cos and finding the GCF but keep getting stuck. Not sure what to do.
cot(x) = 1/tan(x)
Should be immediate after multiplying top and bottom by tan(x)tan(y)
Converting right to left I mean
Ya
What do I do with the -1 on the cotangent side? Does that turn into -(tanxtany)? The rest is good though
Yeah it does
Seeing as that's what you have on the left, that's exactly what you want
Is this right ?
that -1 there went flying
Lol I forgot to add it in at first
anyway ok first off
tan(2x) is 90°-periodic
and second
solutions (in degrees) to one decimal
What do you mean 90 degrees periodic?
tan(2(x+90°)) = tan(2x)
solutions repeat every 90° rather than every 180° as with tan(1x)
So add 90 and 180 instead of 180 and 360?
Ok I see now
is log(n^3 + 6n^2) => log(n^3) + log(6n^2)
?
no, but log(n^3*6n^2) = log(n^3) + log(6n^2)
maybe they meant greater-than-or-equal-to?
Eh, maybe?
Maybe they don't know the convention?
"Equal to or greater than" isn't wrong but peopke dont say it
To be fair, I didn't even know that != means 'not equal' lel
I think it's more likely they were misusing implication
Well that's borrowed from computer languages, not math
Anyone online?
#precalculus for number five, how do I write this mapping it rule?
@viscid thistle which sub-question are you finding difficult?
Firstly, you did correct to notice that it is a decay function. Still you have drawn growth
Don't they say the formula in the first line
@valid violet precisely.
Horizontal and vertical something?
Horisontal stretch and vertical stretch
Oh okay
Then there are also horisontal/vertical translations
Yes
I don't think you can precisely show stretch in a graph paper unless you put many points and sketch it
So you should be able to take care of translations mainly.
For that, you have to find intercepts, asymptotes
No he wants the final graph of this though. I added my own graph for my own reference for help
But they're stretches I just don't know what the exact values are
Inverse of coefficient of x tells how much the graph is stretched
1/2 in this example
Oh I see
So since there is a 2 that is made to 1/2?
For example, graph of e^x reaches value e at x=1. But graph of e^{2x} reaches value e at x=1/2. So it is compressed in a way.
Or stretched by 1/2
Like this
Or, compare e^{x/2}
Ask yourself
The point (x,y) on the unstretched curve
Corresponds to (?,?) On the stretched curve?
That's how i think of it
If that confuses you ignore it
If your original graph is exp(-x), yes.
But if you are drawing exp(x). There is a negative stretch as well
Which means, graph is flipped
Ok I will apply the neg but what about a value of 2?
I'm sorry I'm taking your time, I've been working on this for a while now
We can leave whenever we want, you're not keeping osc here :)
Hahah
So from 3^{-x} to 3^{-(x-1)}, how would you proceed?
Sure
Yes

Hpw would you go from 3^{-(x-1)} to 3^{-2(x-1)}
What's ry?
So can you draw it?
@viscid thistle I edited the original text. So there won't be any ry
Ok
Please send the plots if possible so I can understand that you are following it
Ok I need to get graphing paper one second
Rough sketches will work
Also, now that I know your terminology, I understand what you have written with pencil on your paper and it looks correct.
You can draw final graph with that information.
Also I put it into a graphing calculator and got a y-intercept of 4 but I'm getting a y-incept of 3
@gentle vigil
Btw thanks for all of your help!
How are you getting 3?
What procedure are you following?
@viscid thistle you are welcome!
@gentle vigil
Isnt it 2^3?
You have 3 as the base, not 2
Yup. I thought everything was to the power of 3
I can guarantee that I won't forget that mistake on a test
I hope you do well!
Tysm! @gentle vigil
You're welcome!
hello, can someone help me ? i have to show that this function is odd
yup
or maybe not
question
i showed that it was not even, but playing with power gives me nothing
yeah
4x + 2
oh
@trim fable it like 2^(2x) = 8
i mean that's how multiplication works
ok i got the answer yay
LOL
😛
yeah
so its like
2(2x+1)
u know how sometimes u
only multiply the first
in what case?
you always distribute it
bonsoir haha. when i try -f(x) = f(-x), it's just not the same expression
i'm talking about the exponential function
8^x > 0 for any real x that's what i mean
ofc the exponent could be negative here
att tu peux pas sortir la puissance comme ça là
tu fais comme si $$-x+\sqrt{1+x^2} = \sqrt{-x+1+x^2}$$
emeric75:
ya le petit trick avec les conjugués qui marche bien ici
yes
j'vais test, merci !
@trim fable first you simplify the 9 and 27 to 3 to the power of whatever
I guess you would get 2x/5 = 3
9 = 3^2
27 = 3*3
and when you multiply the 2 by x/5, you actually only multiply the x and do not multiply the 5 by 2
for example if you multiplied 4 by 1/2, you would get 4/2 and not 4/8
yeah it's when you're multiplying by a fraction
yeah
if it's x(y+z) then you distribute
le trick du conjugué me mène nulle part je crois, une autre idée ? @spring thunder
so then u get
j'en ai pas d'autre tbh
yikes
2x/5=3
mais je sais que le conjugué marche
2x=15?
je l'ai fait avec ptdr
yes
x=15/2?
yup
arf bah j'ai pas réussi à l'utiliser pour montrer l'imparité alors
$$\frac{(-x+\sqrt{1+x^2})(x+\sqrt{1+x^2})}{x+\sqrt{1+x^2}}$$
emeric75:
for 1/27
yes, that is correct
jusque la j'suis d'accord
yeah it's 2
what was the original problem?
du coup j'suis débile c'est bon, merci ! @spring thunder
👌
Is this correct? finding the inverse
follow their recommendation/instructions
i dont think that is right
really?
show your work
stop right there
you can't multiply into exponents like that
by same base, they want you to convert that 4 to a base of 2
THEN you can multiply them together
parentheses
that works
factorise 2^(x+2)
well to be more specific,
factorise 2^(x+2) - 2^x
ye and u get
how are you getting that?
do those terms have a common factor?
just like the last question, you can multiply/divide into/out of expenents like that
oh
essentially you just implied that a^anything = a
oh
a^m * a^n = a^(m+n)
oh
can someone name a function with zeros at every integer
$f(x)\equiv 0$
gfauxpas:
preferably something that can be expressed in y= form
$y \equiv 0$
gfauxpas:
https://math.stackexchange.com/questions/3468897/finding-log-ef-in-terms-of-log-ab-and-log-cd
Can someone help me with this?
this is a pointless venture
@viscid thistle I'm trying to figure out what you're doing, but just can't see it
either way
replace 10 with the base?
basically what you did was just set x = z, then say x = z
which is true
When finding the modulus you do √x^2+y^2 what about when the y is just -i would't that just be -1?
modulus of 0+1i is sqrt(0^2 + 1^2)
modulus is scalar
no direction
it's taking the absolute value of the distance from the origin on the complex plane

can ya all help mEH! :C
Well
Bc millenials cant afford to have kids?
just started log and i got quiz tom
Log1?
Well the population is growing
100+1.5/100?
And when it grows you have your orginal population 1, Plus the extra population .015
Why are you dividing?
to get the decimal value? :idk:
Oh
Well 1.5% is equal to 0.015
Adding it too 1 gets you 1.015
And then you just graph the function
idk if i really helped tbh
Explain to me how this simplification happen..
$\sqrt{\frac{21}{25}}=\frac{\sqrt{21}}5$
Icy001:
?
thats how math work
I'll help you answer my question, is that what happened?
yep
Great
Descartes:
cool!
uh... 1/|a|
Yes but I will assume that they will give nice roots and I dont want to be overly confusing to someone who probably isnt comfortable with absolute value
much better to state the conditions otherwise it may cause problems down the line
if you were to avoid abs vals, state that for a>0
Well I agree in principle but I do feel that someone who is not comfortable with how a square root works may be confused by too much info
I may be wrong on that but I am just a guy on discord, not a teacher
Plus/minus is important
I guess teaching early math isnt my calling
In any case from the question they had I would be surprised if they deal with roots of anything but natural numbers at this time
Teaching at their level is also a big deal, so I see no fault in not giving full details right now. They will learn it later down the line, but for now we want to show the concept without getting bogged down in the details.
±
so i'm wondering how do know if the derivative of a function is positive or negative or sometimes both?
does anyone have a link or table that explains this?
like x^4 is bigger than x^2.
x^2 is bigger than -(x^6)
but if you start having more complicated functions like x^5-e^x-sin(x)........
how would you know the derivative of the function is negative or positive?
Well
If f(x) is your function
Then calculate f'(x) and set f'(x) < 0 or f'(x) > 0, depending on what you're trying to calculate.
Then, solve the inequality.
Sometimes, it's hard to solve the inequality, though. So, you can draw a diagram or a graph and just look at its behaviour to find out where it is negative and where it is positive.
thank you.
Need urgent help guys
ok whats the question

wow wulfgar is a mathematician
Umm ok?
Lel, @glad shadow you needed urgent help but it’s been about 3 hours.
@heady jewel he didn't really come across as a mathematician in the books @cursive river
I dont understand the reference 
Oh, he's a character in the Legend of Drizzt series by R A Salvatore
Wulfgar, son of Beornegar, of the tribe of the elk
Oh right lol, I get told my name is in multiple things but I actually just made the name up when I was a kid
Skyrim npc is probably named after Salvatore, i took it as a little easter egg
Yes
Oof noice noice
real quick, how do slant asymptotes work?
by dividing numerator by denominator
isnt it just 17 + 10(417 - 1)?
So 417 = A_20
?? I mean, i just noticed that the terms generally consist of multiples of 10 + 17
So actually, we can write it as:
417 = 17 + 10*40
Ye
Thanks
You can simplify it however you like lol. It’s trivial anyways
The formula should generate the entire series
Mmmh yea
im having trouble finding the inverse of this
$x-\frac{1}{2}=\frac{1}{y^2}$ I got to this step dont know what to do from here
The-Elite:
Combine the LHS into one fraction
$\frac{2x-1}{2}=\frac{1}{y^2}$ okay
The-Elite:
that's very invertible
square root
Well, i wouldn't do that quite yet
hmm
a flip
Ooh
idk
Flip both sides
wait why
Try it and you'll see why
ok
what property is this
i didn't know you just switch fractions like that
oh nvm
ok thx
i got it
But more generally
If two things are equal
You can treat them.the same
That's not worded very well
Hey guys, So when I find the angle between two vectors,
if the angle is 90 degrees it is orthogonal
and if the angle is 0 degrees it is parallel?
Nub question.
but why usn;t the interval for increase surrounded by brackets?
(obv not on inf, but for actual values we know will happen)
Oh. I get it.
Cause at that exact point that's where it stops increasing/decreasing, right?
ok ty
If two vectors are multiplied to each other they then become scalars?
You can't multiply vectors
If you dot product two vectors, you get a scalar though
@patent beacon so what is |v|^2
Is it considered a scalar product because, the result of getting a magnitude from a vector is a scalar?
And now that I remember that would make sense because, the definition of a scalar is that it has magnitude only and not direction
You can think of a scalar as a real number.
Then vectors as arrows
There's a lot of ways to relate these two things
Alright thanks
So the result from a projection is a vector?
Yes
Ok cool
Hi
do I use properties of logarithm here?
a^log base a ^ x = x
cant get my head around what's going on with question b 😦
$a^{\log_a x} = x$
ramonov:
yes
I’m doing practice problems for my class and I am stuck in this question. I can calculate it up myself, but I am trying to figure out how to get it without counting all the way up
until further information is given, i'm going to assume that all you are given is the first 4 terms \textbf{and nothing else}, which means $a_{14} = 19$
Ann:
Well by the way it seems, it looks like it divides by two since it goes from 10 to 5, 5 to 5/2 and so on, so I don’t think it can equal 19
@harsh cipher the question is already in the form of that log property
work isn't needed and you simply just write ||9||
assume it's geometric.
what's the expression for the nth term of a geometric sequence!
(in terms of initial a and ratio r)
How does the left part transform into the right one?
Why not do this like I originally did (I know there are some Xs left to reduce)?
might be a bit less efficient depending on the goal.
also you need to check your signs
its just splitting up the fraction
in the original example
and also cancelling an X out in the second half
$\frac{x^2}{x^4}$ is one result
Botnuke:
-(1+x)(2x) \neq -2x + 2x^3
What relationship must be met so that log_45 [40sqrt(3)] = log_3n [4n]
x(1-2) -2 to -3? how?
x(1-2) to -1 how?
don't divide fractions s like that
Doesn't this x get eliminated by reduction?
what reduction?
look (1-2)x = -x right
with the denominator x^3
yes
so numerator is -x-2 still
cause x is not distributed to the other 2 outside of the parenthesis
so you cannot eliminate x from top and bottom
I see
Then I get (-x-2)/x^3
The initial question remains though. How did they split the fraction resulting in two different denominators?
$\frac{x^2-(1+x)(2x)}{x^4} = \frac{x^2}{x^4} - \frac{2x(1+x)}{x^4}$
Ann:
Makes it clear now. Thks.
But why did the author choose to leave the final result as a split fraction?
preference
I thought simplification is the goal
And (-x-2)/x^3 looks much simplier
But why did the author choose to leave the final result as a split fraction?
w/o context it's impossible to tell
There isn't much of a context to be found. Just another practice problem from the book
Forget it. Doesn't really matter
How did they get rid of this (1+x)?
distribute
Thks
?
What have you tried?
$(a+b)^3 - 3ab(a+b)$
Ekansh:
Is that the best way to approach this?
Abhijeet Vats:
$(a+b)^2 = a^2 + b^2 + 2ab$
Abhijeet Vats:
Can you use the two equations above? Lmao
Ekansh:
Radicals ewww
Radicals are fun, buddy 🙂
Are you Indian? Lol
Maybe, maybe not.
lol
Guys why does $2x^2 + 8x + 6/x^2 - 1$ only have one verical asymptote
Waterblade:
I thought the bottom can be factored as (x + 1) (x - 1 ) thus a VA at x=1 and x = -1
denominator*
Fk man, i'm so tired I can't even do English properly. That's how much of a dumbass i am.
Okay, Waterblade, let's get down to business. What bottom you talking about?
Don't worry, flynn will help me @fluid shore
Hold on, is the $\frac{6}{x^2}$ the fraction or the entire polynomial over $x^2$?
Abhijeet Vats:
FlynnXD:
Oh wtf
2(x^2 + 4x + 3) ->2(x+1)(x+3) @undone pawn
mm hm
and denominator is (x-1)(x+1)
so as a result, there's no discrepancy at x=-1
since limit exists there
and is finite
np
how do i solve (lnx)^2 + 3lnx = 1 ? not sure how i deal with the (lnx)^2 term :/
Set t=lnx and go from there
thanks!
how am i supposed to get the angle between i + j and i + j -k
dot product definition is one way
what do i do with the extra K
these guys are in 3d space. think of the first guy as having 0k component
@sick lava idk how you got 0.86 but dot product uses cos, and make sure your calculator’s in deg mode
Naisu
how do i convert (-srq3 + i)^6 into exponential form
Know how to convert -sqrt(3)+i to exp form?
^6 is easier to do in exp form so I advise you convert the inner to exp form
how
find r and theta
yes arctan
Vectors are parallel if they have the same direction. Both components of one vector must be in the same ratio to the corresponding components of the parallel vector.
thanks got my final in 20 mins
good luck
Calculate
Find the value of the sum
They have a number associated with each sum that you can get. So, get that number.
nice sigma
Thanks guys! :'D
What am I supposed to do with this?
Ooh I think I know~~ but please help :'l
Eh there’s a formula for finding the sum using the first and last term of the series
I know!
I suggest you derive it first lmao
;_; how do I do that?
Write out a general arithmetic series with initial term a1 and common difference d
I'd don't think I got this right...
Is not the right diference
52 would be the right diference
But it doesn't make sense because A_14 ≠ 146
A_3 = 146
Hello?
Ooooh wait
I made an oopsie
This is 10 times worse
Okay, I have this


@viscid thistle when you divided by 13 why didnt you minus 42 first
you didnt divide 13 to the 42
I didn't know if I had to do the right PEMDAS or the inversed PEMDAS :'(
so cos > 0?
no
So every time I want to solve the left side of a function I need to use inversed PEMDAS
that is inverse sine
oop
@viscid thistle or
whats the difference between 1 / sin and sin
Uhmm okay okay
if a=b then a/13 = b/13
the error you made was like
a = b + 13c
a/13 = b + c
this is not the same
you would do a/13 = b/13 + c
I didn't knew because, I thought you only cancel 13 to 13 and not the whole thing because 13 is just affecting the d
nah when you manipulate equations you wanna take operators to the entirety of both sides
not just choosing some terms of both sides and assuming that's equivalent
7 = 7
7 = 3+4
7/4 = 3 + 4/4 (error: not dividing the 3 by 4 too)
7/4 = 3 + 1
7/4 = 4
7 = 16
@viscid thistle see how the error of not dividing the entirety of both sides of the equation by 4 doesn't keep it equivalent?
7 = 7
7 = 3 + 4
(7)/4 = (3+4)/4
7/4 = 3/4 + 4/4
7/4 = 3/4 + 1
1.75 = 0.75 + 1
1.75 = 1.75
Here we divide the entirety of both sides by 4 and it remains equivalent
@sick lava can you post the question
ah ok
tadders:
oh ok
set up system of equations for n and d with a_n and s_n formula @viscid thistle
oh wao
@sick lava so do you know $\sin{\frac{x}{2}} = \pm \sqrt{\frac{1-\cos{x}}{2}}$
tadders:
right
whats your reason for that
csc > 0?
if 1/f(x) is positive, f(x) is positive too right?
yea?
@sick lava post the question
well i mean
sin(x/2) = \pm sqrt(3/8)
sin(x) > 0
2sin(x/2)cos(x/2) > 0
but cos(x/2) will be \pm too
so both \pm sin(x/2) work for some interval in sin(x)>0
so it would be +-
Eh what’s the question?
^
Am trying this
Am here and 1° I don't know if what am doing is okay 2° I don't know how to continue

Okay, ^^ that complicated
I want the difference
No n, can't do it
@viscid thistle do you know the right answer?
Yeah, there should be 12 n terms adding up to 690
arithmetic series aren't sharp on my memory anymore but i picked the following formula online $Sn = n*(\frac{a1+an}{2})$
🆄🆂🅴🆁🅽🅰🅼🅴:
What n then?
i got n = 12
And how do I get it by myself
you pick that formula
substitute Sn, a1 and an with the values you have
then you solve for n
But am not familiarize with it :'( I can't change that type of thing when I have a midterm on Monday :(
The formula I do for Sn is the following
show me
are you sure that's the only formula you have relating to this topic?
i havent touched on this in a loooong time but i am almost certain that we had a formula like this to determine Sn
let me think
I could use it, but my teacher requires me to understand they reason for every variables to be in it, and I can only explain the one I showed you
I can send you a video explaining the deduction of that formula
You can send it, but I'm not promising anything. Is a midterm...
I did this, but I don't think is possible
I don't see why that formula wouldn't be used in that situation since that it is so straight forward
I'll have a look
I could use it, but I don't feel confident enough to use it in my midterm
Yup, better play it safe
:) am glad you understand
So that n I got seems too much
Yeah, never in a million years
Shouldn't it give me 12 as well?
what do you mean?

I figure it out
Are absolute extrema also relative extrema?
tan x = -8/9; x in quadrant II; find cos x
Im getting 9 / srq145
supposedly thats wrong
Anyone here that can help me with a simplification question
post it
,rotate
I'm guessing every multiple of 4 months the number of rabbits multiples by 3
What you guys think
Yes
so this one is a bit confusing
So it says laber force = L(x)
right
then population is P(x)
nvm
its A
idk why i even asked
well you can recognize that 1 = 3^0
And how can I solve this?
9^(v+2)+5*9^(v+1)=14
isolate 9^v first and hope the rhs is a nice power of 3 i guess
Okay, this is what I've done:
9^v = y
y^2+5y-14=0
D=25+4*14=81
D^(1/2) = 9
y1 = (-5+9)/2 = 2
9^v = 2```
How should I continue?
how did you get the quadratic??
Ann:
$9^{v+2} = 9^v \cdot 9^2$
FlynnXD:
I see, thanks
$\lim_{x\to\infty} \frac{5^x}{e^x} = \infty$ right
CoolShot:
Yus
B is not so much computation as it is thinking about what the problem means
i just need help
it wants to know what values of x (amounts you can cut off) are practical for this situation
for example
can you cut off 100 inches from the box?
my last 3 lines are food for thought for B
so when does the amount cut off become impractical
yep
so then D: (0,5)?
yep


