#help-42

1 messages · Page 114 of 1

granite spade
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@rustic osprey wait sorry one last question

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this is the interval

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pi/8 and 7pi/8

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so n wouldnt work here in this scenario

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correct?

rustic osprey
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yeah I know

granite spade
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just wanted to clarify

rustic osprey
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I was trying to get you to arrive at the general solution and then find all n s.t. it's in the interval

granite spade
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okay

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so that would mean

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besides pi/2

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umm

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wait is that it

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is it just pi/2

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no other values?

rustic osprey
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yeah

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only $n=1$ makes $\frac{n \pi}{2}$ lie in $\left[\frac{\pi}{8}, \frac{7\pi}{8} \right]$

potent lotusBOT
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Civil Service Pigeon

granite spade
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thank you so much

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i will definitely ping you in the future youre the best tutor i had

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LOL

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have a good night!

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.close

calm coralBOT
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granite spade
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oh

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LMFAOAOAOIH

rustic osprey
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most helpers don't like to be pinged individually, myself included

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!noping

calm coralBOT
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Please do not ping individual helpers unprompted.

granite spade
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oh oops

rustic osprey
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we had to make this lol

granite spade
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gotcha

rustic osprey
granite spade
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i wont dont worry

rustic osprey
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a lot of us just auto reject them

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myself included lol

rustic osprey
calm coralBOT
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tall moon
#

let $xy=z^2$ prove that there is always $p,q,r$ where $\gcd(q,r)=1$ and
$$x=pq^2$$
$$y=pr^2$$
$$z=pqr$$

potent lotusBOT
#

Skissue ping4response

tall moon
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this question is wierd im not sure what path i go for

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note p,q,r,x,y,z are natural numbers

calm coralBOT
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@tall moon Has your question been resolved?

wanton wave
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Okay maybe I'm being dumb but I don't think this is true. Isn't this a counterexample?

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(x,y,z) = (8,18,12)

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8*18 = 12^2

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If x = pq^2 = 8, and gcd(p,q)=1, then the only possibility is p=8, q=1.

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But if p=8 and y = pr^2 = 18, then r is not a natural number.

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@tall moon

tall moon
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p=2 q=2 r=3?

wanton wave
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but gcd(p,q)=1

tall moon
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wait

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wait

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wait

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oh its gcd(q,r)=1

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whoops

wanton wave
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oh, that seems more plausible lol

tall moon
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let $xy=z^2$ prove that there is always $p,q,r$ where $\gcd(q,r)=1$ and
$$x=pq^2$$
$$y=pr^2$$
$$z=pqr$$

potent lotusBOT
#

Skissue ping4response

tall moon
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streak of me fucking up the question

calm coralBOT
#

@tall moon Has your question been resolved?

calm coralBOT
#

@tall moon Has your question been resolved?

#
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mossy wigeon
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v_c has higher speed right?

calm coralBOT
graceful dust
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hi

mossy wigeon
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hiii

dark fox
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hiiiii

limpid pilot
mossy wigeon
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idk

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cuz

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im getting a 50% response ofr both

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someone said

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since its elastic they share KE

dark fox
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It is a yes

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Conservation of momentum

swift laurel
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we're not given whether it's elastic, but all we need for the problem is conservation of momentum anyway

swift laurel
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it must be

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you can write v_A and v_C in terms of the initial speed of the ball B, the masses, and the final speed of the ball B to demonstrate that

mossy wigeon
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since the b ball goes back

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the velocity of the ball becomes negative for final therefore the box must have higher velocity

swift laurel
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yes. you can express that mathematically by expressing the initial and final momentum of the system in terms of the variables mentioned above

mossy wigeon
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ah okay

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tyty

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.close

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fleet raptor
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why does it give 1 even though i specified the bounds

fleet raptor
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4-4 = 0 so that lies outside of 1-3 or -1--3

limpid pilot
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this is math server

fleet raptor
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ty

limpid pilot
#

.close

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amber wedge
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How do i determine which is bigger wothout the calculator?

amber wedge
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e^pi and pi^e

onyx plinth
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Generally the one with the larger exponent is greater

remote mural
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No

onyx plinth
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I'm sure e^pi is greater

remote mural
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The maxima of the function x^(1/x) occurs at x = e.

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So e^(1/e) > π^(1/π)

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Hint: After this, you may just do some algebraic manipulation to this inequality.

mortal orbit
onyx plinth
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My bad ,not always true i guess

calm coralBOT
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@amber wedge Has your question been resolved?

calm coralBOT
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remote mural
calm coralBOT
remote mural
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Prove that:
[UA1V] + [A1ZW] = [UA1Z] + [WA1V] = 1/2 [UVWZ]

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Given that UVWZ is a rectangle.

jolly pilot
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area of triangle = 1/2 * base * height?

remote mural
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Yes

jolly pilot
remote mural
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ok

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i will tell the progress

calm coralBOT
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@remote mural Has your question been resolved?

remote mural
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Z26W26 = B27A27
For triangle V26P26Q26, area = 1/2 * V26W26 * P26Q26
For triangle S26V26R26, area = Z26V26 * 1/2 * S26R26
Right? And now the sum = 1/2 (Z26W26)(P26Q26 + S26R26) = 1/2 (B27A27) (S26P26 + R26Q26) right?

remote mural
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.close

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remote mural
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Ok bro

calm coralBOT
#
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vagrant oak
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How do I calculate how many arrangements of n objects are there, if k of them need not to be used

vagrant oak
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Take e.g. a, b, c, d, e, f and say e and f dont need to be used

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so valid arrangements are e.g.:
abcd
abedcf
efabcd
eabcd
bfadc

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I need something efficient

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currently the only way I have is summing up some stuff

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nvm, i optimized something else instead so i might not need this

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yep

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I was calculating all binomial coefficients (n choose i) with 0 < n < some bound and 0 < i < another bound instead of just using pascals triangle. Silly me

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exotic cosmos
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x * sqrt(25 - x^2)

calm coralBOT
exotic cosmos
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to maximize this geometrically we are maximizing the inscribed rectangle in a circle?

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is that true?

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well idk in my mind it kinda makes sense but can someone explain regardless

manic hawk
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Yeah, that's right. You can draw the picture to see it

exotic cosmos
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how?

manic hawk
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Draw a circle

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Draw a rectangle

exotic cosmos
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well that part i get

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i mean sqrt(25 - x^2) is a circle with radius 5

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well only the positive branch

manic hawk
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Maximizing a function and twice the function is the same anyway

exotic cosmos
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and where does the rectangle come into play here

manic hawk
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I don't understand your question

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Are you asking how to maximise it?

exotic cosmos
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no i'm asking how maximizing x * sqrt(25 - x^2) translates to maximizing the rea of a rectangle in a circle

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what's the reasoning for that

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i kinda know that it is the case

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but i can't justify it

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or explain it

manic hawk
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Draw the circle. Draw the rectangle. Label the lengths of the rectangle

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If you write the expression for the area, it's the same function

exotic cosmos
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let x be the width and y be the length then x^2 + y^2 = 25

manic hawk
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Not 100

exotic cosmos
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i mean 25

exotic cosmos
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wait what

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the diameter is 10 though?

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so we have a right triangle with hypotenuse of 10

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no?

manic hawk
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Okay, there are several ways to draw this.

exotic cosmos
manic hawk
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Right triangle with hypotenuse of 10 is fine

exotic cosmos
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yeah so what i wrote before was okay?

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x^2 + y^2 = 100

manic hawk
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No, because that has diameter 20

exotic cosmos
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i'm confused 😭

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am i being dumb

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10^2 = 100

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wait

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okay i'm dumb

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lol

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no

manic hawk
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Radius and diameter are different

exotic cosmos
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i'm talking about the triangle though

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😭

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just the triangle alone

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it's just pythag

manic hawk
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Draw it on coordinate axes

exotic cosmos
manic hawk
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That's not your x and y

exotic cosmos
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uhhh i just gave it some labels

manic hawk
exotic cosmos
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like coordinate geometry free

manic hawk
# exotic cosmos

Until this picture, I had no idea why you were talking about hypotenuses or triangles. You really don't want either in this question.

exotic cosmos
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yeah i was confused too

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i think u were talking about a circle

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and i was talking about pythag lol

manic hawk
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Now you can find the area of that

exotic cosmos
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uhhh i don't know what i'm going for

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the diagonal is again of length 10

manic hawk
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Don't use the diagonal

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Label the positive x-intercept x

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Then find the y-intercept in terms of x

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Then find base and height

exotic cosmos
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okay but then i use half the diagonal

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hmm

manic hawk
manic hawk
manic hawk
exotic cosmos
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yeah that's the height

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the base is x

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but we have 8 of those triangles

manic hawk
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Stop using triangles

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You have 4 of those rectangles

exotic cosmos
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sure if radius is one diagonal of a rectangle

manic hawk
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Maximizing a function is the same as maximizing four times that function

exotic cosmos
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then there's 4 such rectangles

exotic cosmos
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h^2 + b^2 = 100

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100 - b^2 = h^2 -> h = sqrt(100 - b^2)

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area of rectangle is b * sqrt(100 - b^2)

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hmm i need a scaling factor and maybe some factorization

manic hawk
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Replace b=2k

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Yeah, scaling factor

exotic cosmos
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yeah that should work

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2k * sqrt(100 - 4k^2)

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2k * sqrt(4) * sqrt(25 - k^2) = 4k * sqrt(25 - k^2)

exotic cosmos
#

.close

calm coralBOT
#
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calm coralBOT
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red locust
#

i just need help here

calm coralBOT
red locust
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would my c stay as square root of 217

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or do i make it 14.73

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i know it cant be simplified further

manic sandal
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both are correct, i was always taught to keep a square root but it is your choice

red locust
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would i do it like this: (7+√217, -10) or (7+14.73, -10)

red locust
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so when i calculate it

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its same answers right

manic sandal
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yep

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well slightly different because of rounding

red locust
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okay was just confused

manic sandal
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but very very similar

red locust
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this is what i got with 14.73

red locust
solid pollen
#

keep it as sqrt, as further calculating after approximating won't give you the correct result (if you have to use the 'c' after calculating it). Supposing it's a theoretical math class.

red locust
#

thank you so mch

calm coralBOT
#

@red locust Has your question been resolved?

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noble crane
calm coralBOT
mortal orbit
calm coralBOT
# noble crane
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
noble crane
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my fault

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im stuck on why its not zero

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4.) I guess

mortal orbit
#

wdym it's not 0

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you did the ratio test

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you found that 1/R = 0

noble crane
#

it is zero right?

mortal orbit
#

the multiplicative inverse of the radius is 0

noble crane
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the computer homework program is marking 0 wrong

mortal orbit
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because they want the radius itself

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not 1/radius

noble crane
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wouldn't still be zero

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0/2

mortal orbit
#

huh

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1/radius = 0

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radius = infinity

noble crane
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how is it infinity

mortal orbit
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1/infinity = 0

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"1/0" = infinity

noble crane
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oh ok

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i see thanks for clearing it up for me

mortal orbit
#

Just to help you for next times

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instead of computing $\frac 1R = \lim_{n\to \infty} \left |\frac{a_{n+1}}{a_n} \right |$

potent lotusBOT
#

rafilou is not not born in 2003

mortal orbit
#

directly compute $R = \lim_{n\to \infty} \left |\frac{a_{n}}{a_{n+1}} \right |$

potent lotusBOT
#

rafilou is not not born in 2003

mortal orbit
#

if you wanna use the ratio test

mortal orbit
mortal orbit
noble crane
#

how is 1/0 infinity

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if were not taking the limit of r

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its infinity when you take the limit of 1/infinity

mortal orbit
#

?

noble crane
#

though R is just a constant

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yea because you set it equall to lim n ---> oo etc..

mortal orbit
#

if you don't like 1/0

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think of 0 as limit of 1/n as n-> infinity

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then 1/(1/n) = n

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so when n-> infinity

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goes to infinity

noble crane
#

ohhh ok ok I think I get it

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I see thanks

#

.close

calm coralBOT
#
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calm coralBOT
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wintry echo
#

$\lim_{x\to+\infty} \frac{x+1}{\sqrt{x^2+x}-\sqrt{x^2+1}}\cdot\ln(\frac{x+2}{x+3})$

potent smelt
#

you don't need a \ before your +

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$\lim_{x\to+\infty} \frac{x+1}{\sqrt{x^2+x}-\sqrt{x^2+1}}\cdot\ln(\frac{x+2}{x+3})$

potent lotusBOT
#

OmnipotentEntity

#

Wobble

wintry echo
#

Can someone help me

atomic quarry
potent smelt
#

Have you given this a crack yet?

wintry echo
#

For me it's +∞

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I just plug infinity in

atomic quarry
wintry echo
#

What

fleet verge
wintry echo
#

What f mean

fleet verge
#

You have to show your work. “For you it is inf” but in reality is not

wintry echo
#

,w lim_{x\to+\infty} \frac{x+1}{\sqrt{x^2+x}-\sqrt{x^2+1}}\cdot\ln(\frac{x+2}{x+3})

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What

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It's very heavy

fleet verge
wintry echo
#

Heavy blow

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Mmm

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Lemme think

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But if x goes to infinity how does it come out as a negative number

hollow totem
#

the stuff in the log is negative

wintry echo
#

If the functions are positive

hollow totem
#

They aren't

wintry echo
#

The logarithm is defined for x>0 so it is positive

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Like √x

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It has no negative values

hollow totem
#

,w log(1/2)

wintry echo
#

Oh

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But here we are talking about limits

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The limit of the log is in positive numbers

hollow totem
#

No it isn't

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It's 0

wintry echo
#

Wdym

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,w graph ln(x)

hollow totem
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The limit of log(x) as x approaches infinity is infinity

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That's not what you have though

wintry echo
#

Why

hollow totem
#

Because... it's... not there?

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Nowhere in your problem is there a log(x)

wintry echo
#

,w graph ln((x+2)/(x+3))

fleet verge
#

Replace

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(x+2) in the numerator

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With (x+3 -1)

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And split in 2 fractions

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(x+3)/(x+3) -1/(x+3)

wintry echo
#

Mmm

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Can you be more clear?

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Oh no its clear

fleet verge
#

You have 1-1/(x+3)

wintry echo
#

$\ln(1-\frac{1}{x+3})$

potent lotusBOT
#

Wobble

fleet verge
#

This is between 0 and 1

wintry echo
#

Its 0

fleet verge
#

So it will be negative

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Close to 0

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But negative

wintry echo
#

0^-

fleet verge
#

That is why the limit is negative

wintry echo
#

Mmm

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So it wouldn't be 0?

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$0^{-}$

potent lotusBOT
#

Wobble

hollow totem
#

What's "it"

wintry echo
#

Its like -0,00000000000000001

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This should be the notation

hollow totem
wintry echo
atomic quarry
wintry echo
#

Its the notation standard

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I think

hollow totem
#

Not for the output of a limit

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But sure why not

wintry echo
atomic quarry
#

Bro rn

wintry echo
#

But the limit is an inexact evaluation

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Isn't that a swinging thing?

hollow totem
#

no and no

wintry echo
#

Why?

hollow totem
#

Because those words don't even make sense

wintry echo
#

Mmm

#

Anyway

#

I think I'm doing it all wrong

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😓

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With 0^- it will never come to -2

hollow totem
#

what's the limit of -1/x

wintry echo
#

0

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By hopital

hollow totem
#

what's the limit of 2x * -1/x

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No not by lhopital

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You can't apply lhopitals to that

wintry echo
#

Oh okay

wintry echo
hollow totem
#

even though one of the parts has limit 0

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The limit is still -2

atomic quarry
wintry echo
#

But I have a fixed 0

hollow totem
#

What

#

What's a "fixed" 0

wintry echo
#

Which I have 0

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Now anything I do will always return 0

wintry echo
hollow totem
#

What's a fixed zero

wintry echo
#

Oh no

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This is not an exact 0, its like $0-\epsilon$

potent lotusBOT
#

Wobble

hollow totem
#

The limit is 0

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The function itself isn't

wintry echo
#

Wdym

hollow totem
#

The limit is zero

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In both cases

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It's not "0+ε", it's not almost 0 or inexactly zero or 0^- or any of this other stuff which has no mathematical meaning which you keep making up

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It's just zero

wintry echo
#

What

hollow totem
#

THE LIMIT IS ZERO

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of -1/x and also of log((x+2)/(x+3))

wintry echo
#

But

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Why its 0

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Within limits

hollow totem
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wdym without limits

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without limits it's a function, not a number

wintry echo
#

Because a limit cannot be 0^+

#

I mean why

hollow totem
#

Ok nothing you say ever makes any mathematical sense

wintry echo
#

Here it seems my notation is used

atomic quarry
#

Bros are fighting

wintry echo
#

@atomic quarry

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What fight

atomic quarry
#

Me rn

wintry echo
#

Why can't I do anything😭

calm coralBOT
#

@wintry echo Has your question been resolved?

calm coralBOT
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radiant moss
#

confused where to start for this

calm coralBOT
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granite spade
#

Can someone please tell me what I did wrong??

calm coralBOT
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Please don't occupy multiple help channels.

granite spade
#

This was my work

kindred estuary
#

You went from 5 + x^3 on the left to 5x + 3

#

Somehow

granite spade
#

thank you so much!!

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mossy wigeon
#

e right?

calm coralBOT
swift laurel
#

makes sense to me

mossy wigeon
#

ok yt

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west horizon
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west horizon
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potent lotusBOT
golden gulch
#

suppose x and y are nonnegative such that x + y = 20, then consider f(x,y) = x^2 + y^2 and maximize/minimize this using the given

west horizon
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golden gulch
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x+y = 20

west horizon
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potent lotusBOT
golden gulch
#

we have two nonnegative numbers x and y

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they tell us the sum of those is 20

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so

west horizon
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golden gulch
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x + y = 20

west horizon
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golden gulch
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x^2 + y^2 = (x+y)^2 - 2xy

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but x+y = 20

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x^2 + y^2 = 400 - 2xy

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hello

west horizon
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golden gulch
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now we need to maximize it first

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we know since x and y are nonnegative that means x>=0 and y>=0

west horizon
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golden gulch
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(x+y)^2 = x^2 + 2xy + y^2

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i rearranged

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for x^2 + y^2

west horizon
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golden gulch
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because thats what im interested in

west horizon
golden gulch
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so the larger the product is, the smaller x^2 + y^2 will be

west horizon
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golden gulch
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so the maximum of 400 - 2xy is 400

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when x or y = 0

west horizon
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golden gulch
#

now for the minimum

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well i guess we could do

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$\frac{x^2+y^2}{2} \geq xy \implies x^2 + y^2 \geq 2xy$

potent lotusBOT
#

syecko

west horizon
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golden gulch
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and if x^2 + y^2 = 400 - 2xy we have a minimum at equality so xy = 100 or x^2 + y^2 = 200

west horizon
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calm coralBOT
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golden gulch
golden gulch
#

are you supposed to use lagrange multipliers

west horizon
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silver quail
calm coralBOT
silver quail
#

ik the answer i dont know how to solve it

exotic cosmos
#

if you subtract both sides by that you’ll have 0 = 0

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which is true for all real numbers

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0 is excluded cuz well it’s not in the domain of (x^2 + 1)/x

silver quail
#

so why isnt it 1 then

drifting seal
#

🤔

drifting seal
#

$\frac{x^2+1}{x} = \frac{x^2+1}{x}$

potent lotusBOT
exotic cosmos
#

also well they’re identical everywhere except where they’re undefined

drifting seal
#

it’s just a true statement with the added condition that x ≠ 0

exotic cosmos
#

so that’s that too

drifting seal
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x isn’t just 1

silver quail
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oh okay got it

drifting seal
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it’s 2, e, pi, sqrt(2), 10, -13748884 etc

silver quail
#

so anything that doesnt equal 0 is all real numbers

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got it

#

thank you!!

drifting seal
drifting seal
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so if x = 0 then it’s undefined

silver quail
#

ok got it

#

thank u

#

.close

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final scarab
#

using law of cosine must find x

calm coralBOT
final scarab
#

what i have rn is (8)^2 = (a)^2 + (9)^2 - 2(9)(a) cos 60 but idk here to go from there

marsh valley
#

Use law of sines to find the missing angles

#

I guess you could even just use law of sines tbh

final scarab
#

yea but the topic we're on is law of cos so idk if i can use law of sines

#

unless it was like you said where i can use cos after ? idk

marsh valley
#

But yeah I think your method works one sec

final scarab
#

okk

marsh valley
#

cos(60) you can compute yourself

#

But it’s 1/2

final scarab
#

yeye

marsh valley
#

Once you’ve expanded everything it s a quadratic equation in x

final scarab
#

oh dang

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a^2 + a/2 - 17/18 ?

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not getting a clean answer from dat mm

marsh valley
#

It’s a^2 -9a + 17 I think

final scarab
#

yea i tried that too n im still getting a weird number

#

well

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two numbers

#

maybe this isnt the correct method n i should jus do law of sines tbh

#

idk

#

im supposed to use law of cos tho

marsh valley
#

I mean it should work are you really expecting a nice result?

final scarab
#

i mean kinda

#

my professor said we shouldnt be seeing really horrendous numbers

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plus im getting two diff numbers

marsh valley
#

You’ll get different numbers but usually only one makes sense

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In either case there could be multiple answers

final scarab
#

hmm ok

#

alr cool ty

#

.close

calm coralBOT
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calm coralBOT
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west horizon
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west horizon
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drifting seal
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yes

west horizon
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potent lotusBOT
west horizon
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drifting seal
#

well, why would you start with x^2 + y^2 = 20?

#

are those your two nonnegative numbers?

west horizon
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drifting seal
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did you make them squared so they were nonnegative

west horizon
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drifting seal
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why not just use x and y

west horizon
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drifting seal
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it doesn’t say "the sum of the squares of two nonnegative numbers is 20"

west horizon
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drifting seal
drifting seal
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it doesn’t say it’s 20

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it says make it as large as possible

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and as small as possible

west horizon
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drifting seal
west horizon
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drifting seal
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let x and y be the two nonnegative numbers

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the sum of them is x + y

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is means =

west horizon
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drifting seal
#

x + y = 20

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then it says find the numbers x and y if x^2 + y^2 is a maximum

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and then do the same for a minimum

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the sum of the squares is just x^2 + y^2

west horizon
drifting seal
#

yes

west horizon
drifting seal
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mhm

west horizon
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drifting seal
west horizon
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drifting seal
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ok great

#

now there are like 3 ways we can do this

#

but seeing as you’re taking single variable calc

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i guess we’re supposed to just do differentiation

west horizon
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drifting seal
#

this seems so easy with algebra but whatever

west horizon
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drifting seal
#

so

#

let’s consider the expression x^2 + y^2

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what do you want to call it

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s?

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for sum

west horizon
#

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drifting seal
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s = x^2 + y^2

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we want s to be a maximum

west horizon
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drifting seal
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hmm yea why wouldn’t we just use algebra here?

west horizon
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drifting seal
#

$x^2+y^2 = 400 - 2xy$

potent lotusBOT
west horizon
#

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west horizon
drifting seal
west horizon
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drifting seal
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what do they do

west horizon
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drifting seal
#

wdym

west horizon
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drifting seal
#

,rotate

west horizon
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potent lotusBOT
west horizon
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drifting seal
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yea this is a completely separate problem though

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still is optimization

west horizon
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drifting seal
#

yea

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i mean you can use multivariable calc

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🤷🏼‍♂️🤷🏼‍♂️

west horizon
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drifting seal
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$\nabla f = \lambda \nabla g$

potent lotusBOT
drifting seal
#

but you don’t know this

west horizon
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drifting seal
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but let’s do algebra

drifting seal
west horizon
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drifting seal
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$(x+y)^2 = (20)^2$

potent lotusBOT
west horizon
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drifting seal
#

i can show you all 3 ways

west horizon
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drifting seal
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because i squared the x+y

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i squared both sides

west horizon
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drifting seal
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because i want to know about the sum of the squares

west horizon
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drifting seal
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i’m concerned with x^2 + y^2

west horizon
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drifting seal
#

ok the only downside of doing it this way is i don’t think you know inequalities

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do you remember

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$\frac{a+b}{2} \geq \sqrt{ab}$

potent lotusBOT
west horizon
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drifting seal
#

ok then we can do it another way

west horizon
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drifting seal
west horizon
drifting seal
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alright

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so

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if x+y = 20, what is either of them in terms of the other

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isolate x or y

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doesn’t matter

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this way is just boring imo

west horizon
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drifting seal
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but this is how you do optimization problems usually

west horizon
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drifting seal
west horizon
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drifting seal
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so

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then if f(x) = x^2+y^2 and y = (20-x)

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what if f(x)

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only in terms of x

west horizon
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drifting seal
west horizon
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potent lotusBOT
drifting seal
#

mhm

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now differentiate that bitch

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i guess we called it s

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find s’

west horizon
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drifting seal
west horizon
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drifting seal
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it’s supposed to be + btw

west horizon
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drifting seal
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multiply by -1

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since -x

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and power rule of course

west horizon
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drifting seal
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no

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$2x -2(20-x)$

west horizon
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drifting seal
#

yo

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ya know what

west horizon
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potent lotusBOT
drifting seal
west horizon
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drifting seal
#

inside stays the same thouyh

potent lotusBOT
west horizon
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potent lotusBOT
drifting seal
#

yea i forgot the 2

west horizon
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drifting seal
#

so 4x - 40

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s’

west horizon
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drifting seal
#

so set it equal to zero

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x = ?

west horizon
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drifting seal
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s’ = 0

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s’ = 4x - 40

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4x - 40 = 0

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x = ?

west horizon
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drifting seal
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2x - 40 + 2x

west horizon
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drifting seal
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mhm

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which means y = ?

west horizon
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drifting seal
#

right

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but

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we need to analyze further

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is this a min or max

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and why

west horizon
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drifting seal
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use second derivative test

west horizon
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drifting seal
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because we only care about a point

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not an interval

west horizon
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drifting seal
#

yea

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f’’(10) = ?

west horizon
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drifting seal
#

you can

west horizon
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drifting seal
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f’’(10) = 4

west horizon
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drifting seal
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f’’(anything) = 4

west horizon
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drifting seal
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since there’s no input

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like if you plotted

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y = 4

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it’s a horizontal line

west horizon
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drifting seal
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no matter the x input it’s still 4

west horizon
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drifting seal
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is 4 > 0?

west horizon
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drifting seal
#

which means x = 10 is a ?

west horizon
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drifting seal
#

yep

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now for the maximum

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let’s go back to the algebra and common sense

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so

west horizon
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drifting seal
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the big thing about optimization is that we are given CONSTRAINT EQUATIONS

west horizon
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west horizon
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drifting seal
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all good

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didn’t sleep well

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my head feels like empty rn

west horizon
drifting seal
#

yes like for instance x + y = 20 is considered a constraint

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like it’s something that must be satisfied

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but there’s a hidden second constraint equation

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which will give us the maximum

west horizon
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drifting seal
#

can you tell me what it might be

west horizon
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drifting seal
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no

west horizon
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drifting seal
#

so

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an added condition was that they were nonnegative yes?

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meaning

west horizon
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drifting seal
#

$x \geq 0 \quad y \geq 0$

potent lotusBOT
drifting seal
#

these are our added constraints

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coupled with the fact that x+y = 20

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all three must be satisfied

west horizon
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drifting seal
#

so we look for i guess you could say critical points or boundary points whatever

#

which would be when x = 0 or y = 0

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and going back to the algebra i said earlier

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$x^2 + y^2 = 400-2xy$

west horizon
potent lotusBOT
west horizon
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drifting seal
west horizon
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drifting seal
#

and that yields x = 0 or y = 0

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which means

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x^2 + y^2 = 400

west horizon
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drifting seal
#

if either is zero

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so that’s our maximum

west horizon
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drifting seal
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which would be when x = 20 and y = 0 or x = 0 and y = 20

west horizon
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drifting seal
#

so we still didn’t find the minimum

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we only found where it occurred

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at x = 10

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if x = 10 what does y =

#

remember x + y = 20

west horizon
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drifting seal
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yep

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so

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what’s x^2 + y^2

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when both x and y are 10

west horizon
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drifting seal
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mhm

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so minimum is 200

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maximum is 400

west horizon
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drifting seal
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we could’ve done this much simpler imo but this way also works

west horizon
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drifting seal
#

well because you’re learning calculus

west horizon
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drifting seal
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so you’re supposed to use calculus techniques

west horizon
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drifting seal
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fire

west horizon
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drifting seal
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next week

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i’m ding chilling

west horizon
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drifting seal
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but there isn’t that much for me to study

west horizon
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drifting seal
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mostly doing the last hws

drifting seal
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i have a quiz tomorrow

west horizon
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drifting seal
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yo i’ll show you the other way

west horizon
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drifting seal
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or maybe even the calc 3 way

west horizon
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drifting seal
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well

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they both might hurt

west horizon
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drifting seal
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id do the same for maximum btw

west horizon
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drifting seal
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algebra way

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x^2 + y^2 = 400-2xy

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x or y = 0

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max is 400

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for minimum

west horizon
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drifting seal
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$\frac{x^2+y^2}{2} \geq \sqrt{x^2y^2} \implies x^2 + y^2 \geq 2xy$

potent lotusBOT
west horizon
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drifting seal
west horizon
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