#help-27

1 messages · Page 75 of 1

long pasture
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now that since all edges are of the same length

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by some Pythagorean Theorem

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it's not hard to find VH

wicked fractal
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yea alr
got that far

long pasture
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then using cosine, we can find the angle👍

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(tbh, i didnt do the math, so i don't know the final answer :P)

wicked fractal
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DV = CV = BV = AV = y
VH = sqrt(y^2*-a^2)

VOH = 90 degrees

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but thats as far as I get

long pasture
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lets see

wicked fractal
long pasture
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including DV,CV,BV,AV

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get it? XD

wicked fractal
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no
I'm a very slow person blobcry

long pasture
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it's okay 🙂

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that is

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AB=BC=CD=DA=VA=VB=VC=VD=2a

wicked fractal
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OHHH

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OH I GET IT NOW

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jesus why'd that take me so long

wicked fractal
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🙂

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thanks a lot man

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byeee

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.close

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low fossil
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Is this proof by induction fallacious?

T(n) = T(n-1) + n. Prove that T(n) = O(n^2)```
low fossil
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nvm i think its right lol

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loud light
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if we have a group, call it G that is not necessarily finite, and we have that H is a subgroup of G and |G:H|=m, can we conclude that G is finite since |G:H| would be infinite if G was infinte?

loud light
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from the definition, |G:H|, which is the number of (left) cosets of H in G. this doesnt make intuitive sense to me as H is finite

loud light
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hhhhhmmmmm

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not stated, so not necessarily

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So the whole question is.
Let G be an abelian group(possibly infinite) with subgroups H and K such that H is a subgroup of K. Suppose |G:K|=n and |G:H|=m where n|m. Find |K:H|.

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all i need to finish the proof is to prove that G is finite

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if it is finite, then I can use Lagranges theorem and be done

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Note: I used the third isomorphic theorem, simply stating for clarity

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long fog
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half cape
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calc help

devout snowBOT
half cape
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I found h''(x) = f''(g(x)) * (g'(x))^2 + f'(g(x)) * g''(x).

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Since f is concave down, that means f''(x) < 0. So does that mean that f''(g(x)) is < 0?

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<@&286206848099549185>

digital knot
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Yes it does

half cape
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hmm

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also

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it says f is increasing

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So we know that f''(g(x)) is < 0 and (g'(x))^2 > 0 so the product of that is negative. Also, f'(g(x)) > 0 and g''(x) < 0 so the product of that is also negative. Since the sum is negative we have shown h''(x) < 0 and thus concave down.
My only concern is that is f'(g(x)) > 0 or >= 0?

digital knot
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It also says the first derivative is nonzero

half cape
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Yes..

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but

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if we take f(x) = x^3

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f'(x) = 3x^2

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f'(0) = 0

digital knot
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I see your concern. I don’t think there are any functions meeting the criteria where that actually happens, but really you don’t need to check

half cape
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Because for this part of h''(x): f'(g(x)) * g''(x) would I then say that the product is always < 0

digital knot
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Break it down into two cases, f’(g(x)) = 0 and f’(g(x)) > 0

half cape
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because if f''(x) >= 0 then this product would be 0

digital knot
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Right, the first term is less than 0 and the second term is at most 0, so the sum is less than 0

half cape
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Yes but

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lol

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this question is so dumb

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u get what my problem is tho right?

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I don't want to say that f'(g(x)) * g''(x) is < 0

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cuz f'(g(x)) could be 0

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which would make the product 0

digital knot
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Right. But that’s not the only part of h(x). I gtg hope you figure it out

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I meant h’’(x)

half cape
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<@&286206848099549185> can anyone help?

lusty sapphire
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The problem states that f' is never zero

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Do not consider f'=0

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Perfect answer right here

devout snowBOT
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half cape
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calc

devout snowBOT
half cape
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,w points of inflection x\left(\ln\left(x^{2}\right)\right)^{\frac{2}{3}}

half cape
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,w intervals increasing x\left(\ln\left(x^{2}\right)\right)^{\frac{2}{3}}

half cape
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,w what is y when x = 0.9 x\left(\ln\left(x^{2}\right)\right)^{\frac{2}{3}}

half cape
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,w intervals decreasing x\left(\ln\left(x^{2}\right)\right)^{\frac{2}{3}}

lusty sapphire
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@half cape are you trying to find an example function?

half cape
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No I have this function:

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Don't know where is it decreasing

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Can't seem to find that out

lusty sapphire
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I see

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Wild

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Have you found where f'=0 yet?

half cape
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yep

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x = 1/e^2/3

lusty sapphire
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and did you calculate f'' at those points yet?

lusty sapphire
half cape
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yeah

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also -e^(-2/3)

half cape
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only first derivative is

lusty sapphire
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Oh duh I did it backwards

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You are right

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No wait..

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f'=0 will give you critical points, local max or min

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Intervals between critical points will be either increasing or decreasing

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use f''>0 or f''<0 to determine increasing or decreasing between critical points

half cape
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yes

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Is it true that this function has no intervals where it is decreasing?

lusty sapphire
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it has decreasing points

half cape
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hmm so is wolfram trolling?

lusty sapphire
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yes

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It got me too

half cape
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which decreasing intervals did u get?

lusty sapphire
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wolfram is not perfect

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!nosols

devout snowBOT
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As a helper, please do not give out answers that could be copied as a homework solution. Have the student work through the problem themselves and guide them along the way.

lusty sapphire
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sorry

half cape
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I got between -1 and 1 not inclusive

lusty sapphire
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best advice I can offer is ^(2/3) is being interpreted as a complex root

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do cbrt(^2) to keep it as a real root

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This is a tricky problem

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Lots of parts

devout snowBOT
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@half cape Has your question been resolved?

half cape
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.close

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scenic surge
devout snowBOT
scenic surge
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for this series

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im suppose to use

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limit comparison

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but

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idk what

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b_n is suppiose to be

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apparently the answer key says b_n = 1/n^(3/2)

wanton temple
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you're asked to show whether this series is divergent or convergent, right?

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or are you to compute the actual values?

scenic surge
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and i am to use limit comparison test here

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but like

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I dont even know how to get started because

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I dont know what $b_n$ is here

woven radishBOT
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Calc II Victim

scenic surge
sick fulcrum
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try comparing it to 1/n^2 lol

scenic surge
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but why 1/n^2

sick fulcrum
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if that doesnt work tune the p in n^p

scenic surge
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what do u mean by tuning?

sick fulcrum
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Like mess with it

scenic surge
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oh so I just keep messing with it?

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but I should start with

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1/n^2

sick fulcrum
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Sure

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Basically something nice

scenic surge
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ngl doe Idk how I would get to 1/n^(3/2) from there doe

sick fulcrum
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If you calculate a few terms you see it would converge

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So you just find a few terms of like

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1/n^2 and friends

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Yeah if 1/n^2 doesnt work I'll go to 1/n^(3/2) as my next try

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Or 1/n^(5/2)

scenic surge
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OHHH

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wait so like

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lets say I were to start with

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1/n^5 right

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not for this series

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but like sum other series

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and that didnt work

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then I would try

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1/n^4.5 and 1/n^5.5

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as my next b_n right

sick fulcrum
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Usually I start with 1/n^2 because its the first thing I know that converges

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1/n doesnt

wanton temple
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mfw basel problem

scenic surge
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what that mean

sick fulcrum
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np

wanton temple
scenic surge
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ah

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ngl doe wont this be

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mad time consuming

sick fulcrum
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No

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You get used to it

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Kmm if you're not going to contribute to the help don't randomly talk

scenic surge
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could I do something similiar

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here aswell

sick fulcrum
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Yeah of course

scenic surge
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bet thanks

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im going to try it

sick fulcrum
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Calculate a few terms and find some other series to look at

scenic surge
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no matter what I compare it with

sick fulcrum
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What

scenic surge
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oh wait

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is b_n = 1/n^2

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then the limit will be 1

sick fulcrum
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What

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Limit of what

scenic surge
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(a_n * 1/b_n)

sick fulcrum
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What is a_n

scenic surge
sick fulcrum
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I have to go now sorry

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But you actually have the tools you need to figure it out yourself

scenic surge
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I got it

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ye thanks

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i was right

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.close

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median stratus
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can someone help me with this question?

wispy hare
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that'll make the equations easier to solve

median stratus
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yes! i have done that

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let me show u

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i dont understand how to get the dialation though

wispy hare
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hmm is there missing info? like the question says it passes through point A and (10, -15/4)

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whats point A

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cuz you need 2 equations to solve for a and b

median stratus
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OH OOPS

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point a is 0,0

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i just realised it was on a seperate sheet

wispy hare
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ah there you go

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💀

median stratus
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so do i do simultaneous

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equations?

wispy hare
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yup

median stratus
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thankyou!!!!

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<33

wispy hare
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all the best!

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maiden zinc
#

i have a function f such as f : Rn[x] -> Rn[x]
f is invective

Since dim Rn[x] < +infinite
So f bijective

I have some doubt about that and if it's really true, then why?
i don't get it

magic thicket
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Think in terms of bases

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Is the image of a basis by f also a basis ?

maiden zinc
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i would say yes

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we do that with matrix

magic thicket
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Try to prove it

maiden zinc
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then (e1, ... e(n+1)) a basis of Rn[x]
f(e1) have the same degree of e1 because it's Rn[x] -> Rn[x]
so (f(e1), ... f(e(n+1)) a basis

magic thicket
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what's the degree of a vector ?

maiden zinc
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degree of what?

magic thicket
maiden zinc
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yes

magic thicket
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that means you've defined what the degree of a vector is

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I'm asking you what that is

maiden zinc
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e1 € Rn[x]
so the same meaning as a polynomial

magic thicket
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oh

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degree as a polynomial

magic thicket
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does it preserve the degree ?

maiden zinc
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hum

magic thicket
maiden zinc
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ok

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then f :E -> E

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with dim E < +infinite

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we have to show that if f injective then f bijective

magic thicket
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dim E = dim F

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otherwise it's not going to work

maiden zinc
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ok

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f injective so f(e1) is not a linear combination of any f(e(i))

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so (f(e1), ... f(e(n)) a basis?

maiden zinc
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well that's no true

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f injective so f(e1) is not equal of any f(e(i))

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but that's not sufficient

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i have to show that it's not a linear combination of any other f(e(i))

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don't know how to do that

magic thicket
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how about showing (f(ei)) is a basis

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directly

maiden zinc
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don't have idea

magic thicket
maiden zinc
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have any advice? x)

magic thicket
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what's easier to use

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as a characterization of injectivity

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f(x) = f(y) => x = y
x != y => f(x) != f(y)

maiden zinc
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ah

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ye so we have e1 != ej => f(ei) != f(ej)

maiden zinc
magic thicket
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one of the strengths of the proof by contradiction is that it gives you a starting point if you otherwise have none

maiden zinc
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if n = dim E
then there's n f(e(i)) so it's a basis since the cardinal is equal to the dimension

magic thicket
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if it's a free family

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ie linearly independent

maiden zinc
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hum

magic thicket
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which you may have seen as saying that a linear combination of them can't be 0 unless it's actually an empty sum

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which amounts to saying one can't be a LC of the others

maiden zinc
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it's remind me nothing

maiden zinc
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ok

magic thicket
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write it out

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use the fact f is linear

magic thicket
maiden zinc
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ye think so

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so f linear so f(e(i)) is a free family basically?

magic thicket
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no

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the zero function is linear

magic thicket
maiden zinc
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that f(e(i)) are linearly dependent?

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that theyre link

magic thicket
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write it out

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write some sort of equality

maiden zinc
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sry i have to go i'll come back

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and write it out :p

devout snowBOT
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@maiden zinc Has your question been resolved?

maiden zinc
magic thicket
#

what does it mean for f(e1) to a linear combination of the f(ei) ?

maiden zinc
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of the e1?

magic thicket
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of the f(ei), i.e. (f(e2), ..., f(en+1))

maiden zinc
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that f(e(i)) = a * f(e1) + ... + a(n+1)*f(e(n+1))

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if that's true they're not free

magic thicket
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need to point that out somehow

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so wlog f(e1) is a CL of the others that way it's just [2, n+1]

maiden zinc
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wlog?

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or just log

magic thicket
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without loss of generality

maiden zinc
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ok that's why i didn't get it

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[2, n+1] why

magic thicket
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suppose f(e1) is a CL of the others

maiden zinc
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ye

magic thicket
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the others are the f(ei), i in [2, n+1]

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which is more convenient than [1, n+1] \ {i} for a fixed i

maiden zinc
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i don't get why inside a set with max n+1 honestly

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but it's not the main point

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so here you showed what?

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you wanna show that it's a free family right

magic thicket
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yes

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by contradiction

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to have a starting point

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since you otherwise couldn't find one

maiden zinc
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ok but don't see where's the contradiction

magic thicket
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you didn't even actually start yet

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$f(e_1) = \sum_{k=2}^{n+1} a_k f(e_k)$

woven radishBOT
#

mateo713

magic thicket
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that's what we assume to reason by contradiction

maiden zinc
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ok and how can i find a contradiction, we just have the information that f is linear and injective

magic thicket
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use linearity

maiden zinc
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$f(e1) = \sum b_k e_k = \sum a_k f(e_k)$

magic thicket
woven radishBOT
magic thicket
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i.e. the units are wrong

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because the ek and f(ek) don't exist in the same space

maiden zinc
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hum no idea

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ah wait

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$f(e1) = f(\sum b_k e_k )= \sum a_k f(e_k)$

woven radishBOT
maiden zinc
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not true since e(i) is a basis

magic thicket
#

that's linearity

magic thicket
maiden zinc
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$f(e1) = f(\sum a_k e_k )= \sum a_k f(e_k)$

woven radishBOT
magic thicket
#

the last one is useless

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it's the step in between

magic thicket
#

then we use the other fact we know

maiden zinc
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that f is injective so e1 != sum of ak*ek

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so contradiction

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the family is free

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so the familie is free and the cardinal is equal to the dimension so it's a basis

maiden zinc
magic thicket
#

you just did

magic thicket
maiden zinc
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ye it's basis

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but i have to show the bijectivity

magic thicket
#

note: you actually showed something a bit more general:
linear injective functions preserve linear independence

magic thicket
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they're a basis

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but now I gotta go

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hopefully you'll be able to convince yourself without me

maiden zinc
#

ye thx a lot

devout snowBOT
#

@maiden zinc Has your question been resolved?

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orchid glade
#

how do i go about looking for sum of this series

orchid glade
#

1+n+n(n-1)/2!+n(n-1)(n-2)/3!.......

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up to nth term

magic thicket
#

that's the sum of the (n choose k) for k ranging from 0 to n
which is known to be 2^n by the expansion of (1+1)^n using the binomial theorem
Feel free to look up any term you've never heard before

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(n choose k) being a binomial coefficient (to look it up more easily)

devout snowBOT
#

@orchid glade Has your question been resolved?

orchid glade
#

i was trying to show the number of subsets of a set with n members is that

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thanks

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scenic surge
devout snowBOT
scenic surge
#

can someone explain how to approach this

devout snowBOT
#

@scenic surge Has your question been resolved?

vast rain
#

probably should try using some test on it

trail eagle
#

Or could it be possible by comparison to the geometric series (7x)^n?

devout snowBOT
#

@scenic surge Has your question been resolved?

scenic surge
vast rain
#

try a few of them

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see what happens

scenic surge
#

wow im so stupid

#

ty

#

.close

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maiden zinc
#

i have E a subspace at finished dimension, let's call n = dim E
and u a linear function of E -> E

i have ker u^k include in ker u^(k+1)
(u^k = it's the combination meaning. ie u^3 = u(u(u(x)))

i have to show that it exists a p€N such as ker u^p = ker u^(p+1)

maiden zinc
#

i think that what make this expression true is that the dimension of E is finished

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since ker u^k is growing the dimension of ker u^(k+1) is at least +1 grower

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so it'll arrive a time when dim ker u^k will be equal to dim E and so the next one will be 0 because it can't be bigger than E

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is my reasoning true?

devout snowBOT
#

@maiden zinc Has your question been resolved?

maiden zinc
#

<@&286206848099549185>

magic thicket
#

Yes

#

Exercise: prove/disprove the property for infinite dimension

#

Hint/answer: ||it's false||

vast rain
#

infinite dimensions don't exist

#

infinity is fake news

#

all numbers are less than 2^128

clever mist
#

why 2^128

magic thicket
#

This is 1984 buddy

#

16 bits before 2000

maiden zinc
#

i don't get it, it works for finite dimension right?

vast rain
#

yes

maiden zinc
magic thicket
devout snowBOT
#

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kindred sedge
devout snowBOT
kindred sedge
#

how

#

i tried division

#

but i dont know how to plug it into the solution

restive river
#

factor numerator

kindred sedge
#

is the factor 2x^2-x+3

restive river
#

yeah

winter patrol
#

,w expand (x-2)(2x^2-x+3)

kindred sedge
#

so if i factor it it will turn into (x-2) (2x^2-x+3)??

restive river
#

yeah

kindred sedge
#

then i substitute the limit

restive river
#

then cancel out x-2

kindred sedge
#

to x??

#

ohhhhhhhhhhhhhhhhhhhh

#

oaky hold on

#

it gave me 9

restive river
#

,w lim as x-> 2 of (2x^3-5x^2+5x-6)/(x-2)

woven radishBOT
restive river
#

yeah ur correct

kindred sedge
#

thankss again!

#

.close

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little onyx
#

Somebody tell me how OK= csc in the picture

devout snowBOT
#

@little onyx Has your question been resolved?

lusty sapphire
#

csc=1/sin

#

HO=1

#

OA=1

#

OG=sin (by definition)

#

triangle OGA similar to tirangle OHK

#

Thus, OK/OH=OA/OG

#

@little onyx

little onyx
#

Aaah..got it i c

#

Thank u very much

#

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sage socket
devout snowBOT
sage socket
#

So, the value I got for c was an imaginary number.

#

So, I'm not sure why that conclusion is wrong

summer flower
#

It has to do with the definition of MVT

sage socket
#

is an imaginary number a value we can use for c?

summer flower
#

Think of continuity

sage socket
#

okay

pseudo basin
#

the right conclusion would be that mvt is inapplicable

#

since your function isn't even defined at x=3, and if it was, it would be guaranteed discontinuous there

sage socket
#

okay

#

but why

#

oh

#

wait so if I plugged in 3

#

ohhhh derp

summer flower
#

The C is irrelevant given that your function doesn’t meet the first requirement of MVT.

sage socket
#

because it's not continuous on that interval?

summer flower
#

Yes

sage socket
#

gotcha

#

cause it is differentiable

#

but it fails the first one

#

yeah okay okay

#

alrighty

#

ty everyone

#

.close

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finite briar
#

What's the general procedure to solving functional equations? For example, f(0.8) = 7/3, f(2) = 13/3. How would I solve this one?

winter patrol
#

depends if you're given more information

magic thicket
#

That's not quite a functional equation I think.
That's more like "how do I extrapolate that"

finite briar
finite briar
magic thicket
#

It's so far from unique

violet wind
#

There's no simpler description of the set of functions that satisfy those equations

pseudo basin
#

f(x) = 7/3 if x=0.8, 13/3 if x=2, 42069 otherwise

magic thicket
#

You've got an infinity of polynomials, of trig functions, etc

pseudo basin
#

@finite briar are you 110% certain that you are given zero further information

finite briar
pseudo basin
#

"about"?

#

okay, no, this won't do.

#

show us the problem exactly as it was stated.

#

screenshot or picture.

#

or tell us you are unable to do this.

finite briar
#

But the function or its derivative haven't been stated

#

Wait a sec

pseudo basin
#

OH MY GOD.

winter patrol
#

show everything under the question number regardless of whether you think its relevant

devout snowBOT
#

@finite briar Has your question been resolved?

finite briar
sage burrow
#

i cant see a task where you should determine a function. you should shade an area and select a part of the graph which represents something

sage burrow
finite briar
#

Find how far the travels in the first 4 seconds..
Isn't that the integral from 0 to 4 of this graph?

finite briar
sage burrow
#

it is the integral, yes. but you are not asked zto calculate it. you are asked to shade the area which represents this.

finite briar
#

Oh...oops ig

pseudo basin
#

in the future be mindful of the xy problem

finite briar
#

But okay, say they asked me to calculate it, how would I do so?

finite briar
pseudo basin
#

...

#

you wanna edit that?

finite briar
#

OH Shit

#

Sorryyy

#

I am very sorry..

sage burrow
finite briar
#

Ah..is there no way to derive the function using the graph?

pseudo basin
#

no

finite briar
#

Sad 😦

sage burrow
#

not exactly. you could assume it looks like a log (or something else) and fit the log, but this is alos an estimation.

finite briar
#

.close

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#
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spice saffron
#

Hey! a^2 + 8a + 12, solve by splitting middle term

spice saffron
#

Kindly help

rotund heron
#

!status

devout snowBOT
#
What step are you on?
1. I don't know where to begin
2. I have begun but got stuck midway
3. I got an answer but I'm told it's wrong
4. I got an answer and would like my work checked
5. I have a question about someone else's worked solution
6. None of the above
rotund heron
#

Does that say “solve” ??

spice saffron
#

I'm on 2

rotund heron
#

Okay, show what you’ve done so far. But wdym “solve”

#

It’s not an equation

#

Do you mean factorise

spice saffron
#

Correct.

#

Factorize

rotund heron
#

Alright can you Show your work?

spice saffron
#

one sec

#

$a * c = 6$

woven radishBOT
spice saffron
#

$-3x -2 = -5, +6$

woven radishBOT
spice saffron
#

oops

#

wrong question

rotund heron
rotund heron
spice saffron
rotund heron
#

Why are you using ‘y’

spice saffron
#

uhh

rotund heron
#

Should that not be 6a and 2a

spice saffron
#

good question

#

right.

#

right it should be a

rotund heron
#

Okay so $a^2 + 6a + 2a + 12$

woven radishBOT
spice saffron
#

but like

#

I can't take common in everything

#

which is how we are told to factorize

rotund heron
spice saffron
#

like

#

take a number outta the bracket

#

but i cant do that here

#

Right?

rotund heron
#

You can

#

What’s common between a^2 and 6a ??

spice saffron
#

a

#

but a is not common in 12

#

oh hold up

rotund heron
#

And what about 2a and 12?

spice saffron
#

i get it now

rotund heron
#

So what do you get as answer?

spice saffron
#

(a+2) (a+6)

rotund heron
#

Yess

spice saffron
#

gg thx but

rotund heron
#

Nice work

rotund heron
spice saffron
#

nvm figured out the next q too

#

thx

rotund heron
#

Lol nice

spice saffron
#

actually

#

can i take a minus sign inside a bracket

#

if not then why

rotund heron
#

Show me what you mean

spice saffron
#

$a^2 -3a -2a -6$

#

$a(a-3) -2 (a-3)$

#

can i do that or is that wrong?

woven radishBOT
rotund heron
#

You can do that

woven radishBOT
spice saffron
#

really

spice saffron
#

its manipulating -2

#

why?

#

soo

#

The answer to a^2 -5a +6

#

is?

winter patrol
#

factoring -2 out of -2a - 6 gets you -2(a+3) and not -2(a-3)

rotund heron
winter patrol
#

they're both factorable, in slightly different ways

spice saffron
#

I see

#

Eh lets get to the last question here

#

y^2 +18y +17

#

I see I can't like split the middle term here

rotund heron
#

Can

spice saffron
#

how

#

a * c = 17

#

17 is prime.

winter patrol
#

so?

#

that makes it easier

#

to determine if there's a nice factorisation

spice saffron
#

but how?

#

product should be 18y correct

#

and 17 should be the sum

winter patrol
#

no

#

no

#

you've got them mixed up

spice saffron
#

what?

#

oh alright

woven radishBOT
#

ℝamonov

spice saffron
#

so 18 should be sum

#

and 17 should be product

winter patrol
#

yes

spice saffron
#

oh!!!

#

17*1

#

lol im dumb

#

Hey

#

x^2 -6x +8

devout snowBOT
#

@spice saffron Has your question been resolved?

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safe turret
#

Indices

devout snowBOT
safe turret
#

Need help with B part

devout snowBOT
#

@safe turret Has your question been resolved?

safe turret
#

im gonna fail math

devout snowBOT
#

@safe turret Has your question been resolved?

safe turret
#

.close

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light quail
devout snowBOT
light quail
#

ok so i got to here

#

should the bottom 2 look different?

#

after i found that my function is = to 0 at x=6

#

i plug in numbers on either side of 6 into my original function to figure out if its a maximum or minimum

#

<@&286206848099549185> invite me your private chat

#

i dont understand why im being targeted

#

@frosty cradle is a good man, maybe he can help

frosty cradle
#

what is your question?

#

(and don't ping individuals in general...)

light quail
#

ok

#

so

light quail
#

and that gave me my picture up top with the black boxes

#

im not sure if i set it up correctly

frosty cradle
#

your picture isn't very clear, the writing is pretty light

light quail
#

and what the numbers mean

#

ok one sec

frosty cradle
#

well what's the original problem?

light quail
#

and i got N = 6

frosty cradle
#

what is the green box?

light quail
#

the derivative

#

they wrote it differently but the graybox is my answer which is also correct

frosty cradle
#

ok then N=6 seems right. is it actually wrong?

light quail
#

nope n = 6 is correct

#

so i plug in a 7 and 5 into original function to determine if its max or min

light quail
#

at the bottom

#

im curious if its done wrong or if i just dont know how to interpret it

#

to know if it goes from negative to pos or vice versa

frosty cradle
#

the "proper" thing to do is calculate the second derivative and see whether it is positive or negative

#

but you have to square the whole denominator, anyway

light quail
#

hmm that would be a very big quotient rule setup i think?

#

oh ur right

#

ok so i got k5/3,721 and k7/7,225

#

now what does this mean for my min and max?

light quail
#

they are both positive

#

what does it mean if they are both positive?

devout snowBOT
#

@light quail Has your question been resolved?

frosty cradle
#

sry

light quail
#

thats ok

frosty cradle
#

both positive? then perhaps N=6 is an inflection point

#

so you'd need to verify with the 2nd derivative

light quail
#

differentiate that?

#

what will happen to that kN^2 ?

frosty cradle
#

yes, or just assume it's an inflection point

#

,w plot (N / (36 + N^2))

light quail
#

what do i do next if i assume its an inflection point?

frosty cradle
#

,w plot (2N) / (36 + N^2)

light quail
#

im not sure how you were able to plot that

light quail
#

hmmm

frosty cradle
#

,w plot (36 - N^2) / (36 + N^2)^2

frosty cradle
#

according to this, at N=7 the derivative is negative, not positive

#

(for k=1)

#

,w plot (72 - 2*N^2) / (36 + N^2)^2

frosty cradle
#

ok, I see where you went wrong. You have to evaluate $f'(5)$ and $f'(7)$, whereas it looks like you evaluated the original functions

woven radishBOT
#

cwatson

light quail
#

oh

frosty cradle
#

$f'(N) = \frac{k(36 - N^2)}{(36 + N^2)^2}$

woven radishBOT
#

cwatson

light quail
#

can i also just plug in 5 and 7 into

frosty cradle
#

into what?

light quail
#

the derivative of the original function

frosty cradle
#

yes, that's what I'm saying

light quail
#

ok so i got f'(5) = 11k/3,721 and f'(7) = -13k/7,225

#

so its positive when its approaching 0

#

and the negative after

#

which means its a maximum

frosty cradle
#

yes

light quail
#

ok there we go

#

now

#

what is expected of me here

frosty cradle
#

is it not just n=6?

light quail
#

wow

#

why would it ask me it like that

#

n = 6 is right

frosty cradle
#

I don't know, seems confusing

light quail
#

thank you

#

.close

devout snowBOT
#
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magic dust
#

I was given

devout snowBOT
magic dust
#

and asked to prove

#

I proved that it is correct

#

but now I'm asked to prove given what I found previously that

#

and I've been trying for like an hour but I can't seem to grasp where to even begin

prime basin
#

You've basically shown it already

#

because 3 < sqrt(11) < 4

#

and 1 < sqrt(3) < 2

magic dust
#

the problem is the goal is they want me to get to exactly the same inequality

#

and I'm not sure how cause for all I know they chose random number to fill in and I will be lucky to find them

prime basin
#

i'm a bit confused as to what you mean

magic dust
#

What I'm expected to do is prove this inequality for those specific numbers

#

and not just say that it's true cause 0.1 is less than 1/6

#

or wait

#

that actually makes no sense when I think about it

#

Okay I think I got it hate my language

#

thanks.

#

.close

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#
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graceful jackal
#

I need help with this

devout snowBOT
gusty sparrow
#

!status

devout snowBOT
#
What step are you on?
1. I don't know where to begin
2. I have begun but got stuck midway
3. I got an answer but I'm told it's wrong
4. I got an answer and would like my work checked
5. I have a question about someone else's worked solution
6. None of the above
gusty sparrow
#

@graceful jackal

graceful jackal
#

Ya

graceful jackal
#

1

gusty sparrow
#

Do you know the formula for area of trapezoid?

graceful jackal
#

And also 3

#

A=bh?

gusty sparrow
#

umm no

graceful jackal
#

Idk than

gusty sparrow
#

$$ A = \frac{a+b}{2}h $$

woven radishBOT
gusty sparrow
#

where a and b are the sides of the trapezoid and h is the height

naive comet
#

1/2 (a+b)h

#

The parallel sides

#

Are a and b

#

Parallel lengths

#

14.9 and 8.3

graceful jackal
#

So I plug the numbers in Using that formula?

gusty sparrow
naive comet
#

Ye

graceful jackal
#

104.4

#

Tysm

#

Another one please

pearl moon
#

Use trapezoid formula for total qre

#

Area

#

And tag me when you answer

graceful jackal
#

Alr

#

@pearl moon 84.63

#

I got it

#

Btw

pearl moon
#

Subtract the area of rectangle in between

graceful jackal
#

Need help with this one

pearl moon
#

Oh ok

#

Wait

#

Use angle enclosed formula

#

Find angle between two sides

graceful jackal
#

Idk what that is

pearl moon
#

Then use trigonometry

#

Hmm

#

(N-2)×180

pearl moon
graceful jackal
#

So N is 5

pearl moon
#

Is that a 5 sided polygon

#

?

graceful jackal
#

No

pearl moon
#

Then how can n be 5

graceful jackal
#

Sorry it’s 12

pearl moon
#

Ok correct

#

Now do the formula

#

And divide it by number of angles

#

Which is 12 too

#

1800/12

#

Tag me when you reply

graceful jackal
#

@pearl moon 150

pearl moon
#

Ok 150/2is the angle between radius and segment

#

Ami right?

#

Do you know trigonometry reply with tag

graceful jackal
#

@pearl moon yes Ik trig but not expert at it

devout snowBOT
#

@graceful jackal Has your question been resolved?

devout snowBOT
#

@graceful jackal Has your question been resolved?

devout snowBOT
#
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• Be polite and have a nice day!

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restive river
#

can a differentiable function exist with no local minima between two local maxima

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#

@restive river Has your question been resolved?

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pine plinth
#

In how many ways can you fill 36 tiles with 2 white pieces , 3 black pieces and an infinite number of purple pieces ?

pine plinth
#

I don't know how to aproach this one. My first guess would have been 12* 36! but apparently that isn't among the answers by a long shot

proud perch
#

hmm

#

does order matter?

#

like is white then purple different from purple then white?

pine plinth
#

that's the thing , I have no idea

#

this is the list of options

topaz axle
#

you choose where white pieces are, and choose where purple pieces are, accounting for some empty space filled by white

#

so not e, not f

pine plinth
#

A refers to non repeating permutations in this textbook, and C to non repeating combinations

topaz axle
#

no clue lol

pine plinth
#

:))))))

#

same

#

should I ping ?

topaz axle
#

it's maybe A

#

nope

#

ok i'll calculate all of them just in case

#

oh right it's a

#

10 is 5C2

pine plinth
#

oooooooooooh

topaz axle
#

you choose 5 non purple spots, and then choose 2 white

pine plinth
#

that makes so much sense

#

thank you !

#

.close

devout snowBOT
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sage socket
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clever mist
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!status

devout snowBOT
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What step are you on?
1. I don't know where to begin
2. I have begun but got stuck midway
3. I got an answer but I'm told it's wrong
4. I got an answer and would like my work checked
5. I have a question about someone else's worked solution
6. None of the above
magic pine
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the following:

sage socket
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what

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So, I'm still struggling with these concave questions

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and inflection points

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I've watched a few videos and read from different books

clever mist
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ok what is concave

sage socket
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oh, like concavity

clever mist
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yeah

sage socket
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well most examples just talked about this
and the second derivative

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But here, I don't have the equation

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So, I'm really not sure how I'm supposed to apply it other than just looking at the shape of the graph

clever mist
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i would just look at the graph

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no need for the math stuff

sage socket
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right

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well that's my problem right now

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I'm not getting it

clever mist
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concave

sage socket
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yeah not super sure what I'm supposed to get from this.

clever mist
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ok

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want an example?

sage socket
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sure

magic pine
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i see concavity as where the function “opens up to”
don’t know if that helps

sage socket
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yeah my professor made a similar statment

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here is where the graph holds water and where it empties it

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I get the idea

clever mist
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if the line is below

sage socket
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but I don't think I'm sure where the intervals are supposed to start and end I guess?

clever mist
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concave?

sage socket
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concave downward ?

clever mist
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yeah

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and if it goes up

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concave upward

sage socket
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if it's above the graph it concaves upward yeah

clever mist
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wha

sage socket
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the tangnet line

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isn't that what you drew

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oh wait

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it's the second deriv

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not the tangent line

clever mist
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i just drew the thing

sage socket
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okie

clever mist
sage socket
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okie

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following

clever mist
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thats how i would solve it

sage socket
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well

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okay

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If I wanted to use the intervals, would I said, it concaves down at (0,1),(1,2) ?

clever mist
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yeah

sage socket
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how about the inflection point?

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here

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I thought it would be at x = 2

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so the coordinates would be (2,3)

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oh the inflection point was correct

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I just didn't need the ()

sage socket
clever mist
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sorry

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:/

sage socket
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cause like what is the blue line supposed to be again

clever mist
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just a line

sage socket
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okay it's just a line

clever mist
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if it is under

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it is concave

sage socket
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ohhhhhh

clever mist
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lol

sage socket
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huh

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if the blue line is under the red, there is a concave?

clever mist
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red line under blue

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concave

sage socket
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so

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is there no concavity at like 4-6?

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.close

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pine fox
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pine fox
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i'm a little unsure how to start this question

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should i just apply the transformation to the basis vectors in B

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how do i ensure that the range ends up being a linear combination of vectors in the set D

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@pine fox Has your question been resolved?

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@pine fox Has your question been resolved?

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@pine fox Has your question been resolved?

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@pine fox Has your question been resolved?

pearl moon
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. close

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.close

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restive river
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Not sure how to solve this.. something about telescoping rule?

restive river
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read this conversation

upper schooner
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Swear down every time that keisuke posts something, it gets asked by someone else moments later catThimc

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indigo zinc
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indigo zinc
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just 25)c

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I took values of x in the range: -2, 1, 0, 4, 5

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ans indicates that 4 is the best possible value for x, since I get y as 5

clever mist
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??

chrome girder
indigo zinc
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got it