#help-38

1 messages · Page 135 of 1

wraith hinge
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😭

supple copper
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,w characteristic polynomial of ((2,0,1);(2,1,3);(1,-1,0))

wraith hinge
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i got the same

supple copper
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,w factorise -x^3 +3x^2-4x + 3

wraith hinge
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bruh

supple copper
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Try this

wraith hinge
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i dont get it

supple copper
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Well you can always just stick A into the function

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Find A² - 5A + 6I

wraith hinge
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yea but

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i just dont wanna do it the normal way

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we're meant to solve this question using characteristic equation

trim joltBOT
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@wraith hinge Has your question been resolved?

trim joltBOT
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@wraith hinge Has your question been resolved?

trim joltBOT
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@wraith hinge Has your question been resolved?

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Channel closed

Closed by @fiery yacht

Use .reopen if this was a mistake.

wraith hinge
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.reopen

trim joltBOT
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trim joltBOT
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@wraith hinge Has your question been resolved?

fair bison
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Huh, this is weird. It doesn't seem like the polynomial f has much to do with the characteristic polynomial of A.

trim joltBOT
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Channel closed

Closed due to timeout

Use .reopen if this was a mistake.

trim joltBOT
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Available help channel!

Send your question here to claim the channel.

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Ask your math question in a clear, concise manner.
Show your work, and if possible, explain where you are stuck.
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urban copper
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,tex \begin{enumerate}
\item Find all values of $a > 0$ such that the area enclosed by the line $y = a$ and the graph of $f(x) = 4x^3 + 12ax^2 + a$ is equal to $3a^2$.
\end{enumerate}

solid kilnBOT
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938c2cc0dcc05f2b68c4287040cfcf71

verbal stream
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!status

trim joltBOT
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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 was told that it's wrong.
4. I got an answer and would like my work checked.
5. I have a question about someone else's work/solution.
6. I have completed the problem and don't need help anymore. Thank you.
7. None of the above
urban copper
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1

vivid glade
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just roleplay as someone finding the area as enclosed

urban copper
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okay

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,, \int a - \int b

solid kilnBOT
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938c2cc0dcc05f2b68c4287040cfcf71

vivid glade
urban copper
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mmm

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its one definite integral minus the other definite integrals

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problem is I dont have a range for the boundaries of the integral

vivid glade
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this is a good concern

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how do you establish boundaries?

trim joltBOT
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@urban copper Has your question been resolved?

urban copper
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im not sure

trim joltBOT
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@urban copper Has your question been resolved?

urban copper
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<@&286206848099549185>

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someone help my fat ass

sudden mist
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First consider drawing a crude sketch of the curves in a graph

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Maybe given certain values of a

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Then what you want to find is the area enclosed, and as such the intersection between the curves (which are reasonable)

urban copper
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okay

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how to do it

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I dont have access to calculator only pen and pencil

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@sudden mist

sudden mist
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Yeah so how would you usually sketch a curve in a graph?

urban copper
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never done it

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how do i do it

sudden mist
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When you say never? Do you mean you’ve never even plotted points before? As that might be a start

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But say, y=a

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This you can surely sketch given a reasonable value for a?

urban copper
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im newbie

sudden mist
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Why are you dealing with integrals when you’ve not even dealt with such things before?

urban copper
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well y=a is a line that passes through a but idk

sudden mist
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Or for that matter the undergrad role assigned?!

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Hm, okay let’s try doing this without a graph

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It will be a very big handicap for us

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But let’s try I suppose

urban copper
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sure

sudden mist
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So we can straight off try and find the intersections for both curves

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How would you do that?

urban copper
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equate them

sudden mist
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Right! Try and do so and show what you arrive at

urban copper
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?

sudden mist
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What?

urban copper
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,, 4x^3 + 12ax^2 + a = a \iff x^2(12a + 4x) = 0

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this?

sudden mist
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Yeah what else would have I meant?

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Hm wait no

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No!

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Yes

urban copper
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now what

sudden mist
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Solve for x

solid kilnBOT
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938c2cc0dcc05f2b68c4287040cfcf71

sudden mist
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Well maybe I’m being harsh, but it’s not at all clear what you need help with here if you’re not willing to explain

urban copper
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?

sudden mist
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This was meant towards your deleted wolfram message

urban copper
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,align &\implies 4x^3 + 12ax^2 + a = a \ &\iff x^2(12a + 4x) = 0 \ &\iff \begin{cases} x_1 = 0 \ x_2 : 12a + 4x = 0 \implies x = -3a \end{cases}

solid kilnBOT
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938c2cc0dcc05f2b68c4287040cfcf71

sudden mist
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Okay, so now that we know the intersections for the x-coordinate we can try to continue

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Since a>0

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We can make the reasonable assumption that the enclosed area must be wherever x is non-positive, since the question states there is one and we’ve just seen where these curves intersects

urban copper
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?

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assumption?

sudden mist
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We can try to show this more carefully but I think it’s clear for our purposes

sudden mist
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Furthermore, we can show that the curve y=a will be under the other curve

urban copper
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i dont get it

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?

sudden mist
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Which part?

urban copper
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how

urban copper
sudden mist
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Yeah that’s what I was about to ask

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Can you see how?

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(Try and do it)

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I’m not here to spoon feed you all the answers

urban copper
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I cant

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i need more help

sudden mist
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Okay so we want to show that 4x^3 + 12ax^2 + a > a for x in between -3a and 0

urban copper
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sure

sudden mist
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In other words, 4x^3 + 12ax^2 > 0

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Try and see if this true for the given x

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And remember a>0

sudden mist
urban copper
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i need more handholding

sudden mist
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Oh Ok so you’re just trolling?

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Lmao why’d you delete the message?

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I think Im done helping here.

urban copper
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ye

proper kernel
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you first need to find out where y = 4x^3 + 12ax^2 + a and y = a intersect

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do you know how to do that

urban copper
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sure

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,, 4x^3 + 12ax^2 + a = a \ \iff 4x^3 + 12ax^2 = 0

proper kernel
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you mean $4x^3+12ax^2+a=a$

solid kilnBOT
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938c2cc0dcc05f2b68c4287040cfcf71

proper kernel
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@urban copper are you stuck

urban copper
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yes

proper kernel
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try factoring

urban copper
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sure

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,, 4x^3 + 12ax^2 = 0 \implies 4x^2(x + 3a)

solid kilnBOT
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938c2cc0dcc05f2b68c4287040cfcf71

proper kernel
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is it 4x or 4x^2

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youre also forgetting the = 0 at the end

urban copper
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,, 4x^3 + 12ax^2 = 0 \implies 4x^2(x + 3a) = 0

proper kernel
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with that done, what are the solutions to the equation

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@urban copper you have 4 * x^2 * (x + 3a) = 0

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for them to multiply to 0, that would mean at least one of the factors is 0

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that means 4, x^2, or (x + 3a)

urban copper
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is it me lr

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or

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the latex bot

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,, 4x^3 + 12ax^2 = 0 \implies 4x^2(x + 3a) = 0

proper kernel
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youre a bit preoccupied it looks like

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I can wait

urban copper
proper kernel
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you now have the equation 4x^2(x + 3a) = 0
what are the solutions to this equation?

urban copper
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well

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either 4x^2 = 0 or x + 3a = 0

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so x1 = 0

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x2 = -3a

proper kernel
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so the intersections are at x1 = 0 and x2 = -3a

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the area lies between these intersections

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so which intersection is the left end of the area?

urban copper
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-3a

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because a>0

proper kernel
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thats correct

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the right end of the area ends at 0

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so horizontally, this area spans from -3a to 0

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vertically, this area is bounded by y = a and y = 4x^3 + 12ax^2 + a

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which one is at the top?

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(one of them will always be on the top and the other one always be at the bottom, so you can test out values of a and x to see which one it is)

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@urban copper are you stuck again

urban copper
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second one is on the top

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we can graph them to be sure

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but i only have access to pen and paper

proper kernel
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I told you to test out values, did you do that?

urban copper
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i did

proper kernel
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did it confirm that the second one is on the top?

urban copper
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yeah

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is using random values a rigurous proof?

proper kernel
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what do you think value testing is for in calculus?

urban copper
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unsure tbh

proper kernel
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youve seen that y = 4x^3 + 12ax^2 + a and y = a only intersect in two places

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so that means, between x = -3a and x = 0, that one of them is always on top and the other is always on the bottom

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compared to other methods, just placing in numbers for a and x will show which one is on top

proper kernel
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its also easier to just compare numbers than having to judge 4x^3 + 12ax^2 + a's behavior

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are you with me so far?

urban copper
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no

proper kernel
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do you want to elaborate?

urban copper
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how do I know which one wins

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one is more bigger than the other

proper kernel
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I told you the "how" already

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you mean why, right?

urban copper
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sure

proper kernel
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Im going to assume you didnt test the values properly

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lets try some values like a = 1

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that would mean y = 4x^3 + 12x^2 + 1 and y = 1

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now we know the intersections are between x = -3 and x = 0

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from using a = 1 with -3a and 0

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I didnt use any theorems

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dont delete your comments

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thats bad practice to hide your mistakes

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anyways, I can then test x = -1 to see which one is higher

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y = 4(-1)^3 + 12(-1)^2 + 1 = -4 + 12 + 1 = 9

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so we've seen that y = 4x^3 + 12x^2 + 1 is higher than y = 1 at a=1, x=-1

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are you with me so far?

urban copper
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x=-1?

proper kernel
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it doesnt matter which value of x I test

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so long as that value is between x=-3 and x=0,

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this value would be within the region where the area should be

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and in that region, either 4x^3 + 12x^2 + 1 or 1 is higher

proper kernel
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are we ready to continue?

urban copper
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okay

proper kernel
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now lets use a property
not a theorem yet, just a property

urban copper
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i was just confused because you used a = 1 and x = -1 but okay

proper kernel
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dont read into it too much

urban copper
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it was just too abrupt

proper kernel
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everyone moves at a different speed, dont worry aobut it

urban copper
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sure

proper kernel
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anyways
in general, we know that both y = 4x^3 + 12ax^2 + a and y = a are both continuous

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continuity promises some nice things, one of them being IVT

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continuity is still there if I set a = 1, so y = 4x^3 + 12x^2 + 1 and y = 1

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now we've seen that they intersect only at x = -3 and x = 0

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they can't intersect anywhere else

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still with me?

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(I havent gotten to anything important yet, just asking)

urban copper
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yes

proper kernel
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now at x = -3 and x = 0, y = 4x^3 + 12x^2 + 1 and y = 1 are at the same height

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(they intersect)

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at x = -1, y = 4x^3 + 12x^2 + 1 is higher

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lets assume that at x0, y = 4x^3 + 12x^2 + 1 is lower

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with the additional restriction that -3 < x0 < 0

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if this x0 is found, we would be able to prove that just testing one value isnt enough to rule the entire -3 < x < 0 region as "y = 4x^3 + 12x^2 + 1 is higher"

proper kernel
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however, that would mean it would need to cross y = 1

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which can only happen at x = -3 and x = 0

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so the only way 4x^3 + 12x^2 + 1 can be below y = 1 at x = x0 is if x0 is outside of -3 < x < 0

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since x0 can never be inside -3 < x < 0, that means y = 4x^3 + 12x^2 + 1 is always above y = 1 in the region -3 < x < 0

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do you understand so far?

urban copper
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sure

proper kernel
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not a yes

urban copper
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how does ivt come into play

proper kernel
urban copper
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i agree

proper kernel
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IVT never comes into play, because you didnt ask for a formal proof

proper kernel
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since continuity already is pretty clear visually, you dont need a proof to see how the proof would work

urban copper
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how to prove

proper kernel
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there you go

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you need to keep that rigor throughout next time

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now do you remember IVT?

urban copper
proper kernel
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yep

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now a more general proof shouldnt need to depend on a = 1

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I chose it as an example, so lets let a > 0 instead

proper kernel
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so instead you can read that as "continuous on [b, d]"

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now with a being general, we found the intersections of y = 4x^3 + 12ax^2 + a and y = a at x = -3a and x = 0

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now as before, I test a value out and do x = -a

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since a > 0, then -a < 0,
since 1 < 3, then a < 3a, so -a > -3a
hence -3a < -a < 0

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so x = -a is inside (-3a, 0)

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do you understand so far?

proper kernel
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still not a yes

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anyways lets see what happens if x = -a is tested

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y = 4(-a)^3 + 12a(-a)^2 + a
y = -4a^3 + 12a^3 + a
y = 8a^3 + a

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since a > 0, 8a^3 > 0
adding a to both sides, 8a^3 + a > a

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y = 8a^3 + a is greater than y = a

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so y = 4x^3 + 12ax^2 + a is higher than y = a at x = -a

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do you get that?

urban copper
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sure

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i get it

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it’s a yes

proper kernel
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you can also just say the word "yes"

urban copper
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ye

proper kernel
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because the word "sure" is a universal sign of sarcasm so you cant use it in a legit way unless said in person

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in short, I dont hear the tone you use when you use it

proper kernel
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the theorem here assumes that b < d, so Ill need to repeat this again for when d < b

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we know f(b) = f(-a) > a

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if f(x) dips below y = a, then f(x) would < a

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so lets assume f(d) < a

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now let k = a

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by IVT, there exists a constant in [b, d] = [-a, d] such that f(c) = k = a

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however if f(c) = a, then y = f(x) and y = a intersect at x = c

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but since -3 < -a = b < c < d < 0, c is not -3 nor 0

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this would prove that c is somehow a third intersection which cannot happen, since we've already seen f(x) only intersects with a at x = -3a and x = 0

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(also if f(d) = a, then the same "third intersection occurs but with x = d, so f(d) = a cannot happen)

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so by contradiction, f(d) > a

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so f(x) > a for all x in [-a, 0)

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do you understand?

urban copper
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too much words and little latex gimme a minute to read

proper kernel
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alr
latex would make this harder since you dont get to parse grammar

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if you want, I can give you a latex version, but by the time I finish you'd probably get what I typed

urban copper
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I would appreciate it i am not in a hurry btw and i enjoy math

proper kernel
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can you read $\forall$ and $\exists$?

solid kilnBOT
urban copper
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universal and existencial quantifiers?

proper kernel
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you have them swapped (yea thats correct)

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and theyre read "for all" and "there exists"

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anyways the latex here is going to use a lot of these since theyre short

proper kernel
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@urban copper here you go

urban copper
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assume there exists d in (-a, 0)?

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why

proper kernel
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yes, I said earlier that the IVT is a bit one-sided

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it assumes b < d

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I then would have to post a similar proof for when d < b

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the proof is very similar in that other than changing d < b, none of the machinery changes, so its not worth posting two very similar images if focusing on reading one is good enough

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when you understand this proof, Ill post the second one

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I also said earlier to change [a, b] to [b, d]

proper kernel
proper kernel
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you can see how similar these are

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brb

proper kernel
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@urban copper back, you here?

trim joltBOT
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@urban copper Has your question been resolved?

urban copper
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here

proper kernel
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did you read the proofs?

urban copper
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only first one

proper kernel
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you still need time reading them?

urban copper
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I think maybe math is not for me

proper kernel
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formal proof latex is not for you

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mostly because you werent taught formal proof latex

proper kernel
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it has grammar and words to connect nouns and phrases together

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asking for a latex proof has no guarantees of being smoother than the words

urban copper
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fair

proper kernel
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now how familiar are you with IVT

urban copper
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little to nothing

proper kernel
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right, thats not good

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to be able to understand how IVT is used, youll need to be familiar with what its saying

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do you want to get into that or just take as a fact that f(x) > a for all x in (-3a, 0)?

urban copper
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lets assume it

proper kernel
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oh

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then lets move on

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we've verified that the top of the region is always y = 4x^3 + 12ax^2 + a and the bottom is y = a

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it starts on the left at x = -3a and ends on the right at x = 0

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this is enough to write an integral of the region in particular

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do you know how to write that integral?

urban copper
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sure

proper kernel
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sounds good, try it out

urban copper
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,, \int_{-3a}^{0} 4x^3 + 12ax^2 dx - \int_{-3a}^{0} a \ dx

solid kilnBOT
#

938c2cc0dcc05f2b68c4287040cfcf71

proper kernel
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you mean $\int_{-3a}^0(4x^3+12ax^2+a)\dd{x}-\int_{-3a}^0a\dd{x}$

solid kilnBOT
urban copper
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sure

proper kernel
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usually this is memorized as $\int_{-3a}^0((4x^3+12ax^2+a)-(a))\dd{x}$ instead

solid kilnBOT
proper kernel
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so you directly consider it as the difference or gap between the top and bottom

urban copper
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now what

proper kernel
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now you simplify and solve that integral

urban copper
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,align &\implies \int_{-3a}^0\left(4x^3+12ax^2\right)\dd{x} \ &\implies \int_{-3a}^0\left(4x^3\right)\dd{x}+\int_{-3a}^0\left(12ax^2\right)\dd{x}

wraith hinge
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Hi

proper kernel
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Im not sure why you didnt simplify the a - a

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you have an extra \left

solid kilnBOT
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938c2cc0dcc05f2b68c4287040cfcf71

urban copper
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,align &\implies \int_{-3a}^0\left(4x^3+12ax^2\right)\dd{x} \ &\implies \int_{-3a}^0\left(4x^3\right)\dd{x}+\int_{-3a}^0\left(12ax^2\right)\dd{x} \ &\implies \left[ \frac{4x^4}{4} \right]{-3a}^{0} + \left[ \frac{12ax^3}{3}\right]{-3a}^{0}

solid kilnBOT
#

938c2cc0dcc05f2b68c4287040cfcf71

urban copper
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@proper kernel

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can u help

proper kernel
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you should first simplify the expressions inside those brackets

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like the 4/4

urban copper
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,align &\implies \int_{-3a}^0\left(4x^3+12ax^2\right)\dd{x} \ &\implies \int_{-3a}^0\left(4x^3\right)\dd{x}+\int_{-3a}^0\left(12ax^2\right)\dd{x} \ &\implies \left[ \frac{4x^4}{4} \right]{-3a}^{0} + \left[ \frac{12ax^3}{3}\right]{-3a}^{0} \ &\implies \left[0 - \left(-3a\right)^{4}\right] + \left[ 0 - 4a\left(-3a\right)^3\right]

solid kilnBOT
#

938c2cc0dcc05f2b68c4287040cfcf71

proper kernel
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thats correct

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now simplify what you have down there

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youre kidding me

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please do that by hand

urban copper
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,align &\implies \int_{-3a}^0\left(4x^3+12ax^2\right)\dd{x} \ &\implies \int_{-3a}^0\left(4x^3\right)\dd{x}+\int_{-3a}^0\left(12ax^2\right)\dd{x} \ &\implies \left[ \frac{4x^4}{4} \right]{-3a}^{0} + \left[ \frac{12ax^3}{3}\right]{-3a}^{0} \ &\implies \left[0 - \left(-3a\right)^{4}\right] + \left[ 0 - 4a\left(-3a\right)^3\right] \ &\implies -\left(81a^4\right) -4a(-27a^3)

solid kilnBOT
#

938c2cc0dcc05f2b68c4287040cfcf71

proper kernel
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for a timesave, you can split 81 into 3 * 27

urban copper
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sure

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,align &\implies \int_{-3a}^0\left(4x^3+12ax^2\right)\dd{x} \ &\implies \int_{-3a}^0\left(4x^3\right)\dd{x}+\int_{-3a}^0\left(12ax^2\right)\dd{x} \ &\implies \left[ \frac{4x^4}{4} \right]{-3a}^{0} + \left[ \frac{12ax^3}{3}\right]{-3a}^{0} \ &\implies \left[0 - \left(-3a\right)^{4}\right] + \left[ 0 - 4a\left(-3a\right)^3\right] \ &\implies -\left(81a^4\right) -4a(-27a^3) \iff 81 = 3 \times 27 \ &\implies -3(27a^4) -4a(-27a^3)

solid kilnBOT
#

938c2cc0dcc05f2b68c4287040cfcf71

urban copper
#

,align &\implies \int_{-3a}^0\left(4x^3+12ax^2\right)\dd{x} \ &\implies \int_{-3a}^0\left(4x^3\right)\dd{x}+\int_{-3a}^0\left(12ax^2\right)\dd{x} \ &\implies \left[ \frac{4x^4}{4} \right]{-3a}^{0} + \left[ \frac{12ax^3}{3}\right]{-3a}^{0} \ &\implies \left[0 - \left(-3a\right)^{4}\right] + \left[ 0 - 4a\left(-3a\right)^3\right] \ &\implies -\left(81a^4\right) -4a(-27a^3) \iff 81 = 3 \times 27 \ &\implies -3(27a^4) -4a(-27a^3) \ &\implies -3(27a^4) + 4(27a^4) \implies (27a^4)(-3+4)

solid kilnBOT
#

938c2cc0dcc05f2b68c4287040cfcf71

proper kernel
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@urban copper are you going to finish that

urban copper
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I messed up

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can u find mistake or no

proper kernel
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no you didnt

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keep going

urban copper
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okay

#

,align &\implies \int_{-3a}^0\left(4x^3+12ax^2\right)\dd{x} \ &\implies \int_{-3a}^0\left(4x^3\right)\dd{x}+\int_{-3a}^0\left(12ax^2\right)\dd{x} \ &\implies \left[ \frac{4x^4}{4} \right]{-3a}^{0} + \left[ \frac{12ax^3}{3}\right]{-3a}^{0} \ &\implies \left[0 - \left(-3a\right)^{4}\right] + \left[ 0 - 4a\left(-3a\right)^3\right] \ &\implies -\left(81a^4\right) -4a(-27a^3) \iff 81 = 3 \times 27 \ &\implies -3(27a^4) -4a(-27a^3) \ &\implies -3(27a^4) + 4(27a^4) \ &\implies (27a^4)(-3+4) \ &\implies 27a^4

solid kilnBOT
#

938c2cc0dcc05f2b68c4287040cfcf71

proper kernel
#

27a^4 is correct

#

Im pretty sure you mistyped it when you put that into the calculator earlier

#

now you know the area is 27a^4

#

according to the problem, what must this area also be equal to?

urban copper
#

,tex \begin{enumerate}
\item Find all values of $a > 0$ such that the area enclosed by the line $y = a$ and the graph of $f(x) = 4x^3 + 12ax^2 + a$ is equal to $3a^2$.
\end{enumerate}

solid kilnBOT
#

938c2cc0dcc05f2b68c4287040cfcf71

urban copper
#

,align &\iff 27a^4 = 3a^2 \ &\iff a^2 = \frac{3}{27} \ &\iff |a| = \sqrt{\frac{3}{27}} \ &\iff a = \pm \sqrt{\frac{3}{27}}

proper kernel
#

yep, now solve for a

#

not with a calculator

#

thats not ideal

#

try square rooting instead

solid kilnBOT
#

938c2cc0dcc05f2b68c4287040cfcf71

urban copper
#

can u help or no

#

@proper kernel

proper kernel
#

whats 3 / 27?

urban copper
#

sure

#

,align &\iff 27a^4 = 3a^2 \ &\iff a^2 = \frac{3}{27} \ &\iff |a| = \sqrt{\frac{3}{27}} \ &\iff a = \pm \sqrt{\frac{3}{27}} \ &\iff a = \pm \frac{1}{3} \ &a > 0 \implies a = \frac{1}{3}

proper kernel
#

9, not 8

#

they tell you a > 0

#

so what must a be

solid kilnBOT
#

938c2cc0dcc05f2b68c4287040cfcf71

proper kernel
#

yep

#

by coincidence*, when a = 1/3, the area is also 1/3

#

so a, the area, 3a^2, and 27a^4 are all 1/3

proper kernel
#

when you calculate the area knowing a = 1/3, it turns out to be 1/3

urban copper
#

.close

trim joltBOT
#
Channel closed

Closed by @urban copper

Use .reopen if this was a mistake.

#
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urban copper
#

,tex \begin{enumerate}
\item Determine all values of $x \in \mathbb{R}$ for which the series $\sum_{n=1}^\infty \frac{2^n x^n}{n + 5^n}$ is convergent.
\end{enumerate}

solid kilnBOT
#

938c2cc0dcc05f2b68c4287040cfcf71

cyan zinc
#

there's the 'formal' way and then there's the easy way. the easy way is to just see that 2x < 5

urban copper
#

formal I would prefer otherwise my homework solution might not be rigurous enough

#

<@&286206848099549185>

ionic pendant
#

you can use the root or ratio tests

urban copper
#

sure

#

lets use the root one

#

,, L = a_n = \frac{2^n \cdot x^n}{n + 5^n}

solid kilnBOT
#

938c2cc0dcc05f2b68c4287040cfcf71

urban copper
#

,tex [
L = \lim_{n \to \infty} \sqrt[n]{|a_n|}.
]

The Root Test states:
\begin{enumerate}
\item If $L < 1$, then the series $\sum_{n=1}^\infty a_n$ converges absolutely.
\item If $L > 1$, then the series $\sum_{n=1}^\infty a_n$ diverges.
\item If $L = 1$, the test is inconclusive, and the series may converge or diverge.
\end{enumerate}

solid kilnBOT
#

938c2cc0dcc05f2b68c4287040cfcf71

urban copper
#

,align a_n &= \frac{2^n \cdot x^n}{n + 5^n} \ \lim_{n \to \infty} \sqrt[n]{\left|a_n\right|} &= \lim_{n \to \infty} \sqrt[n]{\left|\frac{2^n \cdot x^n}{n + 5^n}\right|}

solid kilnBOT
#

938c2cc0dcc05f2b68c4287040cfcf71

urban copper
#

and we want it to converge

#

,, \lim_{n \to \infty} \sqrt[n]{\left|\frac{2^n \cdot x^n}{n + 5^n}\right|} < 1

solid kilnBOT
#

938c2cc0dcc05f2b68c4287040cfcf71

trim joltBOT
#

@urban copper Has your question been resolved?

urban copper
shell shale
#

wat is x lol

winged hinge
#

squeeze thm

urban copper
solid kilnBOT
#

938c2cc0dcc05f2b68c4287040cfcf71

urban copper
#

@wild quail

#

<@&286206848099549185>

#

@shell shale

#

@winged hinge

#

@ionic pendant

winged hinge
#

use squeeze theorem to find limit

white dagger
urban copper
#

I want to practice ROOT TEST

desert sky
#

Man y'all smart as fuck

#

Idek why I have this role

white dagger
winged hinge
#

yeah use squeeze theorem to find the limit of the sequence in the root test

shell shale
#

i wrote 2 + 2 as 5

#

in one exam

white dagger
urban copper
#

right

white dagger
#

So you can reduce it to $\lim_{n \to \infty} \sqrt[n]{\frac{2^n |x^n|}{n + 5^n}}$

solid kilnBOT
#

Closer

urban copper
#

sure.

#

now what

white dagger
#

And I think you can split case to x >= 0 and x < 0 breadthink

white dagger
urban copper
#

,, \lim_{n \to \infty} \sqrt[n]{\left|\frac{2^n \cdot x^n}{n + 5^n}\right|} < 1 \ \lim_{n \to \infty} \sqrt[n]{\frac{2^n \cdot |x^n|}{n + 5^n}} < 1 \ \lim_{n \to \infty} \frac{\sqrt[n]{2^n \cdot | x^n |}}{\sqrt[n]{n + 5^n}} < 1 \ \lim_{n \to \infty} \left(\sqrt[n]{2^n} \cdot \sqrt[n]{|x|^n}\right) < \lim_{n \to \infty} \left(\sqrt[n]{n + 5^n}\right) \ |x| < \lim_{n \to \infty} \sqrt[n]{n + 5^n}

#

can u help or no

#

@white dagger

white dagger
solid kilnBOT
#

Closer

#

938c2cc0dcc05f2b68c4287040cfcf71

urban copper
#

,, \lim_{n \to \infty} \sqrt[n]{\left|\frac{2^n \cdot x^n}{n + 5^n}\right|} < 1 \ \lim_{n \to \infty} \sqrt[n]{\frac{2^n \cdot |x^n|}{n + 5^n}} < 1 \ \lim_{n \to \infty} \frac{\sqrt[n]{2^n \cdot | x^n |}}{\sqrt[n]{n + 5^n}} < 1 \ \lim_{n \to \infty} \left(\sqrt[n]{2^n} \cdot \sqrt[n]{|x|^n}\right) < \lim_{n \to \infty} \left(\sqrt[n]{n + 5^n}\right) \ 2|x| < \lim_{n \to \infty} \sqrt[n]{n + 5^n} \ 2|x| < \lim_{n \to \infty} \sqrt[n]{5^n\left( 1 + \frac{n}{5^n}\right)}

solid kilnBOT
#

938c2cc0dcc05f2b68c4287040cfcf71

urban copper
#

,align &\lim_{n \to \infty} \sqrt[n]{\left|\frac{2^n \cdot x^n}{n + 5^n}\right|} < 1 \ &\lim_{n \to \infty} \sqrt[n]{\frac{2^n \cdot |x^n|}{n + 5^n}} < 1 \ &\lim_{n \to \infty} \frac{\sqrt[n]{2^n \cdot | x^n |}}{\sqrt[n]{n + 5^n}} < 1 \ &\lim_{n \to \infty} \left(\sqrt[n]{2^n} \cdot \sqrt[n]{|x|^n}\right) < \lim_{n \to \infty} \left(\sqrt[n]{n + 5^n}\right) \ &2|x| < \lim_{n \to \infty} \sqrt[n]{n + 5^n} \ &2|x| < \lim_{n \to \infty} \sqrt[n]{5^n\left( 1 + \frac{n}{5^n}\right)} \ &2|x| < \lim_{n \to \infty} \sqrt[n]{5^n} \cdot \lim_{n \to \infty} \sqrt[n]{\left(1 + \frac{n}{5^n}\right) }

white dagger
solid kilnBOT
#

Closer

white dagger
#

And this will make you go around the circle, though

solid kilnBOT
#

938c2cc0dcc05f2b68c4287040cfcf71

urban copper
white dagger
# urban copper ?

I think you need to use the log trick here which is: $\lim_{n \to \infty}e^{\frac{1}{n} \ln{(n + 5^n)}}$

solid kilnBOT
#

Closer

white dagger
#

And use L'Hopital rule

urban copper
#

let me handle this

#

,align &\lim_{n \to \infty} \sqrt[n]{\left|\frac{2^n \cdot x^n}{n + 5^n}\right|} < 1 \ &\lim_{n \to \infty} \sqrt[n]{\frac{2^n \cdot |x^n|}{n + 5^n}} < 1 \ &\lim_{n \to \infty} \frac{\sqrt[n]{2^n \cdot | x^n |}}{\sqrt[n]{n + 5^n}} < 1 \ &\lim_{n \to \infty} \left(\sqrt[n]{2^n} \cdot \sqrt[n]{|x|^n}\right) < \lim_{n \to \infty} \left(\sqrt[n]{n + 5^n}\right) \ &2|x| < \lim_{n \to \infty} \sqrt[n]{n + 5^n} \ &2|x| < \lim_{n \to \infty} \sqrt[n]{5^n\left( 1 + \frac{n}{5^n}\right)} \ &2|x| < \lim_{n \to \infty} \sqrt[n]{5^n} \cdot \lim_{n \to \infty} \sqrt[n]{\left(1 + \frac{n}{5^n}\right) } \ &|x| < \frac{5}{2} \cdot \lim_{n \to \infty} \sqrt[n]{1 + \frac{n}{5^n}}

solid kilnBOT
#

938c2cc0dcc05f2b68c4287040cfcf71

white dagger
#

I mean: $\lim_{n \to \infty}\sqrt[n]{n + 5^n} = \lim_{n \to \infty}e^{\frac{1}{n} \ln{(n + 5^n)}}$

solid kilnBOT
#

Closer

winged hinge
#

squeeze theorem 1 < 1 + n/5^n < 1 + 5^n/5^n = 2 cat_happycry

urban copper
#

wait I need more handholding

#

im newbie

#

can u explain harder

white dagger
winged hinge
#

Inequality is preserved when u take n-th root and limit of a constant to nth root is 1

urban copper
#

can u help or not

winged hinge
#

do u know squeeze theorem

urban copper
#

y

winged hinge
#

u just can use it to justify why the limit is 1

urban copper
#

u show the latex i can wait

#

,align &\lim_{n \to \infty} \sqrt[n]{\left|\frac{2^n \cdot x^n}{n + 5^n}\right|} < 1 \ &\lim_{n \to \infty} \sqrt[n]{\frac{2^n \cdot |x^n|}{n + 5^n}} < 1 \ &\lim_{n \to \infty} \frac{\sqrt[n]{2^n \cdot | x^n |}}{\sqrt[n]{n + 5^n}} < 1 \ &\lim_{n \to \infty} \left(\sqrt[n]{2^n} \cdot \sqrt[n]{|x|^n}\right) < \lim_{n \to \infty} \left(\sqrt[n]{n + 5^n}\right) \ &2|x| < \lim_{n \to \infty} \sqrt[n]{n + 5^n} \ &2|x| < \lim_{n \to \infty} \sqrt[n]{5^n\left( 1 + \frac{n}{5^n}\right)} \ &2|x| < \lim_{n \to \infty} \sqrt[n]{5^n} \cdot \lim_{n \to \infty} \sqrt[n]{\left(1 + \frac{n}{5^n}\right) } \ &|x| < \frac{5}{2} \cdot \lim_{n \to \infty} \sqrt[n]{1 + \frac{n}{5^n}}

solid kilnBOT
#

938c2cc0dcc05f2b68c4287040cfcf71

winged hinge
#

Basically it says if u have a_n < b_n < c_n and lim a_n = lim c_n, then lim a_n = lim b_n = lim c_n

#

lim of 1^(1/n) is clearly 1

urban copper
#

ok

winged hinge
#

lim of 2^(1/n) is also 1

urban copper
#

,w limit of n to infinity of (1+ n/(5^n))^(1/n)

solid kilnBOT
winged hinge
urban copper
#

okay

#

can u help or

winged hinge
#

yeah I'm tryna remember the full proof lol

urban copper
#

how to find x in R s.t. this shit converges

white dagger
#

$|x| < \frac{5}{2}$ so $\frac{-5}{2} < x < \frac{5}{2}$

solid kilnBOT
#

Closer

urban copper
#

sure

#

so $x \in \left(\frac{-5}{2}, \frac{5}{2}\right)$

solid kilnBOT
#

938c2cc0dcc05f2b68c4287040cfcf71

white dagger
#

And you need to test whether the series convert at endpoint separately

white dagger
solid kilnBOT
#

Closer

white dagger
#

So you need to test it

urban copper
#

can u draw it and show me the latex

winged hinge
#

if a> 1 then a^(1/n) = 1 + b_n for b_n >= 0, so a >=1 + nb_n, so (a - 1)/n >= b_n >= 0, then squeeze theorem implies lim b_n =0 so lim a^(1/n) = 1

white dagger
#

And check whether it converges at those points

urban copper
white dagger
#

Let me latex it

#

$\sum_{n=1}^{\infty} \frac{2^n (\frac{5}{2})^n}{n + 5^n}$ and $\sum_{n=1}^{\infty} \frac{2^n (\frac{-5}{2})^n}{n + 5^n}$

solid kilnBOT
#

Closer

urban copper
#

right

#

second one is alternating

#

due to (-1)^n

#

can someone help or not

#

lets apply root test for left series

#

to determine if it converges or diverges

#

after that we can play with the second one, which looks a little more intimidating

white dagger
#

You don't need root test

urban copper
#

wdym obviously

#

math is never obvious, is sometimes trivial

white dagger
#

Try simply it first

#

$a^n b^n = (ab)^n$

solid kilnBOT
#

Closer

urban copper
#

sure

#

,, \sum_{n = 1}^{\infty} \frac{5^n}{n + 5^n}

solid kilnBOT
#

938c2cc0dcc05f2b68c4287040cfcf71

urban copper
#

so its 1/1

white dagger
#

Obviously it is 1 or you can check with L'Hopital

urban copper
#

factorizing is easier for me

#

I do prefer to avoid lhopi tals

white dagger
#

Ok so it diverges at x = 5/2 so we exclude it

urban copper
#

sure

#

,, \sum{n=1}^{\infty} \frac{2^n (\frac{-5}{2})^n}{n + 5^n}

solid kilnBOT
#

938c2cc0dcc05f2b68c4287040cfcf71

white dagger
#

The second one you can use alternating series test to see that it diverges. So the final result is $x \in (-5/2, 5/2)$

solid kilnBOT
#

Closer

urban copper
#

so its not inclusive

#

because both ends diverge

#

@white dagger

#

so are we done or ?

white dagger
urban copper
#

ahh leibnitz test

#

waitt

#

I need to show both ends diverge

#

can u help or no

white dagger
#

🧐

urban copper
#

how to show it using leibnitz

white dagger
urban copper
#

alternating series test

#

but we need to show it is decreasing sequence

#

can we use lagrange?

white dagger
#

Another condition is: $\lim_{n \to \infty}a_n = 0$

solid kilnBOT
#

Closer

urban copper
#

sure

#

,, \sum_{n=1}^{\infty} \frac{2^n \cdot \left(-1\right)^n \left(\frac{5}{2}\right)^n}{n + 5^n} \ a_n = \frac{2^n \cdot \left(-1\right)^n \left(\frac{5}{2}\right)^n}{n + 5^n}

white dagger
#

$a_n = \frac{5^n}{n + 5^n}$

solid kilnBOT
#

938c2cc0dcc05f2b68c4287040cfcf71

#

Closer

white dagger
#

We don't care about (-1)^n

urban copper
#

wdym

#

$\sum_{n=1}^{\infty} \frac{2^n (\frac{5}{2})^n}{n + 5^n}$ and $\sum_{n=1}^{\infty} \frac{2^n (\frac{-5}{2})^n}{n + 5^n}$

solid kilnBOT
#

938c2cc0dcc05f2b68c4287040cfcf71

urban copper
#

I was talking about the second series

#

I believe you are talking about the first one innit

#

@white dagger

white dagger
#

Then it will become: $\lim_{n \to \infty} (-1)^n \frac{5^n}{n + 5^n}$

solid kilnBOT
#

Closer

urban copper
#

okay

#

then what

#

does (-1)^n diverge or

white dagger
#

Use second condition of alternating series test

urban copper
#

oh it converges to zero

white dagger
#

No it diverges

urban copper
#

wdym

#

pŕove that diverges

#

prove it

white dagger
#

If you have alternating series: $\sum (-1)^n a_n$

solid kilnBOT
#

Closer

white dagger
#

Then for it to converges two conditions need to be satisfied:

#

1 is a_n need to form a decreasing sequence

#

2 is $\lim_{n \to \infty} a_n = 0$

solid kilnBOT
#

Closer

white dagger
#

Condition 2 is often easier to test first

urban copper
#

it’s not zero

#

$\lim_{n \to \infty} (-1)^n \frac{5^n}{n + 5^n}$

solid kilnBOT
#

938c2cc0dcc05f2b68c4287040cfcf71

urban copper
#

can u help

#

@white dagger

white dagger
white dagger
solid kilnBOT
#

Closer

urban copper
#

i know

#

limits is 1

#

,w limit n to infinity(5^n)/(n + 5^n)

solid kilnBOT
urban copper
#

it’s not ZERO

#

<@&286206848099549185>

white dagger
#

Meaning it diverges

urban copper
#

?

#

elaborate

white dagger
#

So -5/2 is excluded as well

urban copper
#

is that a minimum condition

#

for any series

#

i DONT GET IT

#

@white dagger

white dagger
urban copper
#

but first one is not alternating

#

how can u

#

use alternating test for a NOT ALTERNATING SERIES

white dagger
urban copper
#

SECOND ONE DIVERGES SURE

#

WHAT ABOUT FIRST ONE

white dagger
urban copper
#

???

white dagger
#

If $\lim_{n \to \infty} a_n \neq 0$ then it diverges

solid kilnBOT
#

Closer

white dagger
#

That is divergence test

#

I don't use alternating series test for the first one

urban copper
urban copper
#

okay so we are done right

white dagger
solid kilnBOT
#

Closer

urban copper
#

sure

white dagger
#

You can test with Wolfram alpha to be sure

urban copper
#

can u do it for me

#

i am bad with technology

#

can u do it or no

#

@white dagger

white dagger
urban copper
#

,w SumConvergence[(2^n x^n)/(n + 5^n), n]

solid kilnBOT
white dagger
#

Ok so it is true

urban copper
#

,w SumConvergence[(2^n x^n)/(n + 5^n), 1]

solid kilnBOT
urban copper
#

,w SumConvergence[(2^n x^n)/(n + 5^n),n]

solid kilnBOT
trim joltBOT
#

@urban copper Has your question been resolved?

proper kernel
#

I can confirm $x\in\qty(-\frac52,\frac52)$ is the answer, so whats your remaining question

solid kilnBOT
urban copper
#

.close

trim joltBOT
#
Channel closed

Closed by @urban copper

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#
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Remember:
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wraith hinge
trim joltBOT
wraith hinge
#

This YouTube video says to factor a radical you should memorize the perfect squares which I have until 256

#

But when factoring how do I know the multiplication of those larger numbers

#

Do I start guessing with my calculator trying each perfect square

#

Like he shows 36 times 3 = 108

#

How would I know that

proper kernel
#

more practically, you dont memorize that that happens

#

what you do instead is repeatedly divide by potential factors until you break down the whole number

#

for example, I see 108 and its even

#

I try dividing by 2

#

108 = 54 * 2

#

108 = 27 * 2 * 2

#

27 is the third power of 3, I know that

#

108 = 3 * 3 * 3 * 2 * 2

#

108 = 3 * 3 * 3 * 2 * 2

#

then with this, you can see that pairs of the same number naturally form squares

#

3 * 3 * 2 * 2 = 3^2 * 2^2 = 6^2

#

so 108 = 3 * 6^2

#

so sqrt(108) = sqrt(3 * 6^2)

#

= sqrt(3) 6

wraith hinge
#

Wow thank you so much

proper kernel
#

np

wraith hinge
#

I didn’t know that

#

I appreciate your help

#

.close

trim joltBOT
#
Channel closed

Closed by @dark dome

Use .reopen if this was a mistake.

trim joltBOT
#
Available help channel!

Send your question here to claim the channel.

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Ask your math question in a clear, concise manner.
Show your work, and if possible, explain where you are stuck.
After 15 minutes, feel free to ping <@&286206848099549185>.
• Type the command .close to free the channel when you're done.
• Be polite and have a nice day!

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grand shard
#

Can someone help me in understanding the solution by providing a slightly more elaborate explanation?

urban copper
#

well

#

,, \frac{\frac{(n+1)^2}{n^2}}{\frac{1}{n^4}} = \frac{n^4(n+1)^2}{n^2}

solid kilnBOT
#

938c2cc0dcc05f2b68c4287040cfcf71

urban copper
#

but

#

if you take n^8 out of the sqrt is n^4

#

also

#

(n+1)^2 is to the power of two same with n^2

grand shard
#

I got the first step thanks but I'm trying to wrap my mind around why the 2nd step was needed because this kinda seems like it's changing the equation too far than the original, for the limit

urban copper
#

,, \frac{(n+1)^2}{n^2} = \left(\frac{n+1}{n}\right)^2

solid kilnBOT
#

938c2cc0dcc05f2b68c4287040cfcf71

urban copper
#

agree or disagree

grand shard
#

AH THANKS

#

I couldn't figure out such a simple thing in the entire problem smh

#

Thanks a lot man

#

😭🙏

urban copper
#

no worries, keep it hard

grand shard
#

.close

trim joltBOT
#
Channel closed

Closed by @grand shard

Use .reopen if this was a mistake.

trim joltBOT
#
Available help channel!

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Ask your math question in a clear, concise manner.
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atomic seal
#

hi

trim joltBOT
atomic seal
#

lim(x,y)->(0,0) (e^x-e^y)/x-y

#

i found this question somewhere
i asked my sir about it and he said its out of my syllabus yet i wanna know what the limit is

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you can ping me

dusky gust
#

(i haven't done anything like this but i think it is what question is really telling you to do)

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e^y (e^(x-y) - 1) / (x-y)

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so you have t and y

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you get e^y = 1

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and you know what (e^t-1)/t is

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@atomic seal

atomic seal
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oh

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but

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what are you gonna do about e^y

dusky gust
atomic seal
#

oh

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makes sense

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thank you

#

.close

trim joltBOT
#
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trim joltBOT
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urban copper
#

,tex \begin{enumerate}
\item Let ( f ) be a differentiable function that satisfies
[
x^2 f(x) = 3x + \int_{9}^{3x} t f\left(\frac{t}{3}\right) dt.
]
Find the Taylor polynomial of order 2 for ( f ) at ( x_0 = 3 ).

\item Find \( f \) differentiable such that 
\[
f^3(x) f'(x) = 15 x^9 e^{2x^5}, \quad f(0) = 1.
\]

\item Find \( a > 0 \) such that the area of the region enclosed between the graphs of 
\[
f(x) = a \sqrt{x} \quad \text{and} \quad g(x) = x^2 - 10x \quad \text{for} \quad 0 \leq x \leq 9 
\]
is equal to 207.

\item Calculate the radius of convergence of the series 
\[
\sum_{n=1}^{\infty} \left(\frac{n+1}{n+5}\right)^n \left(\frac{n+3}{2^n}\right) x^n.
\]

\end{enumerate}

solid kilnBOT
#

938c2cc0dcc05f2b68c4287040cfcf71

dusky gust
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i think you should try differentiation both sides first

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in 1st question

urban copper
#

twice

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ftc1 required

dusky gust
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2xf + fx^2 = 3 + 3x f - 9f(0)

urban copper
#

can u draw it in latex

dusky gust
urban copper
#

do u have pen and paper

dusky gust
#

i mean i do have, but not camera

urban copper
#

ok, write the latex then

dusky gust
#

what is cmd for @solid kiln

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,, 2xf(x) + x^2f'(x) = 3 + 3x f(x) - 9f(3)

urban copper
#

fix RHS

solid kilnBOT
#

チラチーノ

dusky gust
#

,, f(x) = f(3) + f'(3)(x-3) + 1/2! f''(3)(x-3)^2 + ...

urban copper
#

yeah

#

okay

#

agreed

solid kilnBOT
#

チラチーノ

dusky gust
#

you need taylor polynomial of order 2

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so you can ignore rest of it

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you need f''(3) and f'(3)'s values

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and f(3)

dusky gust
#

you get f(3) = 1/3

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,, \item 2xf(x) + x^2f'(x) = 3 + 3x f(x) - 3
\item 2xf(x) + x^2f'(x) = 3x f(x)

solid kilnBOT
#

チラチーノ
Compile Error! Click the errors reaction for more information.
(You may edit your message to recompile.)

dusky gust
#

,, x^2f'(x) = x f(x)

solid kilnBOT
#

チラチーノ

dusky gust
#

now you put x = 3 here

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,,f'(3) = (3 \times 1/3)/3^2 = 1/9

#

how to write multiply symbol

digital cloak
#

$\times$

solid kilnBOT
#

Pseudonium

dusky gust
#

ok thx

#

you get f'(3) = 1/9

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you already got f(3) = 1/3

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wait my calculations are bad

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let me edit

urban copper
#

please check your calculations

solid kilnBOT
#

チラチーノ

urban copper
dusky gust
#

now looks good

dusky gust
solid kilnBOT
#

チラチーノ

dusky gust
#

you will get f''(3)

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now just put there and you get the expression

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(1st question solved)

urban copper
#

okay

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,w differentiate f(x) * 1/x

solid kilnBOT
urban copper
#

,, f^{(2)}(3) = \frac{3f’(3) - f(3)}{9}

solid kilnBOT
#

938c2cc0dcc05f2b68c4287040cfcf71

urban copper
#

,, f’’(3) = \frac{\frac{1}{3}- f(3)}{9}

#

,, f^{(2)}(3) = \frac{\frac{1}{3}- f(3)}{9}

solid kilnBOT
#

938c2cc0dcc05f2b68c4287040cfcf71

urban copper
#

f’’(3) = 0

trim joltBOT
#

@urban copper Has your question been resolved?

trim joltBOT
#

@urban copper Has your question been resolved?

urban copper
#

<@&286206848099549185>

#

@wild quail

carmine spade
#

dont do that lol

#

ping random mfs

urban copper
#

mb

#

can someone lend me a hand gentlemen?

winged hinge
#

f(3) = 1. $3^2f(3) = 33 + 0$ (integral from 9 to 3*3 = 9 is 0), so f(3) = 1

urban copper
#

do it in latex please

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I will wait

winged hinge
#

nah I'm on mobile lol

solid kilnBOT
#

992DuckEnthusiast (duck eater)

forest vortex
#

@urban copper

urban copper
trim joltBOT
#

@urban copper Has your question been resolved?

fair bison
#

@urban copper what are you working on right now?

#

I'm confused, what part of the question are you stuck on

trim joltBOT
#

@urban copper Has your question been resolved?

trim joltBOT
#
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#
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trim joltBOT
#
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spice granite
#

.close

trim joltBOT
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halcyon stratus
trim joltBOT
halcyon stratus
#

I need solve all questions

dark sundial
#

Have you tried any of them?

#

@halcyon stratus

halcyon stratus
#

I can solve first order equations

#

But I haven’t tried the second order

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I know few methods

dark sundial
#

Have you read your book or lecture notes?

halcyon stratus
#

I’m perfectly good till first order

dark sundial
#

you have to think of functions that have a derivative that is of the same type as the original functions

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the exponential satisfies this requirement

halcyon stratus
#

Am I supposed to know this?

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How did you figure it out

dark sundial
#

If you attended the class of second order odes

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or read the sectian that explains it

halcyon stratus
#

I didn’t attend unfortunately

dark sundial
#

section*

#

I'll show you

halcyon stratus
#

I’m tensed

dark sundial
#

just a second

halcyon stratus
#

4 total problems and the time is running

#

I believe 1B 1C 1D follow the same pattern?

clear cloud
dark sundial
#

then you have to apply the lambda value to the exponential

halcyon stratus
#

Wow

dark sundial
#

but there's a catch

#

you only have 1 possibility for lambda in this equation

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and there's a theorem that states

#

that a second order linear ode has 2 lambdas

halcyon stratus
#

After you found lambda, does the problem complete?

dark sundial
#

not yet

#

there's 1 extra step

#

you need initial conditions

halcyon stratus
#

I feel overwhelmed

dark sundial
#

y0 and y'0

halcyon stratus
#

There are no initial conditions

#

For 1a

dark sundial
#

then all you can say is y(t)=Ae^(3t)+Bte^(3t)

dark sundial
halcyon stratus
#

4 problems

dark sundial
#

it's more than enough

halcyon stratus
#

Really?

dark sundial
#

yes

halcyon stratus
#

But I don’t wanna waste ur time

dark sundial
#

don't worry

#

it's saturday

halcyon stratus
#

Are u okay with helping me throughout the entire assignment?

dark sundial
#

I can help you with some of the questions, the others are just a repetition

halcyon stratus
dark sundial
#

the ode is a linear one

#

so the solution is a linear combination of possible solutions

#

if you had 2 different lambdas you'd have y=Ae^(lambda1)+Be^(lambda2)

#

in the specific case of a repeated lambda, 3 and 3 in the first problem

#

you have to put a t, before the second solution

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the independent variable

halcyon stratus
#

Kinda confusing tbh

dark sundial
#

in this case you have 2 different lambdas

#

yay

halcyon stratus
#

A quadratic always has 2 solutions right ?

dark sundial
#

but they are equal

#

the parabola touches the x axis in just 1 point

#

at the vertex

dark sundial
halcyon stratus
dark sundial
#

yes

halcyon stratus
#

Do bcd follow the same pattern ?

dark sundial
#

yes

dark sundial
# dark sundial

you have to substitute lambda 1 and 2 in the answer I sent you

dark sundial
#

in the cases you have 2 roots

halcyon stratus
dark sundial
#

you're welcome

halcyon stratus
#

I’ll solve bc and send u the solutions

dark sundial
#

differential equations is my favorit topic

halcyon stratus
#

What does graph the solution in interval mean

halcyon stratus
dark sundial
#

and use y0 and y'0 to determine A and B

#

you have a system of linear equations

halcyon stratus
#

I’m here

dark sundial
dark sundial
#

the case where you have a 2nd order ode with 1 root on the polynomial equation is the special case

halcyon stratus
dark sundial
#

you've applied the wrong formula

dark sundial
halcyon stratus
#

After B?

#

Bro I’m pissed

#

Ahhhhh

dark sundial
halcyon stratus
dark sundial
#

solve for A and B and you'll have the answer

dark sundial
#

and plot it

#

I'm helping you and another person, at discord too, in another language, at the same time.

halcyon stratus
#

No worries

dark sundial
#

This is way more exciting than being a teaching assistant, of students who don't even want to attend lectures.

halcyon stratus
#

I hate summer classes

dark sundial
#

But you're asking for help now

dark sundial
halcyon stratus
halcyon stratus
#

Can u give me few mins

#

I need to copy 1a 1B to the answer sheet

#

4 more hours till deadline

dark sundial
#

ok

#

no problem

#

It's still 7:33 pm here in Brazil

halcyon stratus
#

6:33 pm in New York

dark sundial
#

@halcyon stratus finished copying?

halcyon stratus
#

Few more mins please I had some other work

dark sundial
#

ok

halcyon stratus
#

Sorry for making u wait

#

My fucking dasher canceled my order and I haven’t ate anything today

dark sundial
#

this is not healthy

#

go eat something

#

I'm at home

#

We in Brazil generally go to university at the city we live in, with our parents.

halcyon stratus
#

Don’t worry the assignment is important

#

I don’t have time

#

3 and half hours

dark sundial
#

Then, solve it

halcyon stratus
#

Done copying

dark sundial
#

ok

#

great

halcyon stratus
#

I’m moving on to c

dark sundial
#

I'll be dining, if you need any help

#

and I'll be back soon

halcyon stratus
#

no worries thanks for the help

#

I will complete 1abcd

dark sundial
#

I'm done with dinner

trim joltBOT
#

@halcyon stratus Has your question been resolved?

halcyon stratus
#

im having trouble with d

halcyon stratus
dark sundial
#

(-2-i*sqrt(6))/2

#

it's an "i"

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the imaginary root of -1

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@halcyon stratus

halcyon stratus
#

im done with 1

#

i need help with 2,3,4

dark sundial
#

ok

halcyon stratus
#

do u think we have time

dark sundial
#

let me see

#

yes

halcyon stratus
#

2 and half hours more

#

i will be eating i need a break

dark sundial
#

ok

#

I'll be right here

halcyon stratus
#

the complex roots are -1+2i

#

if u figured out 2,3,4 let me know

dark sundial
#

ok

halcyon stratus
#

,afk eating

dark sundial
#

calculating the 3a

halcyon stratus
#

C is solved

dark sundial
#

I belive that in 3a he is using Alpha and Beta instead of A and B as constants