#help-38

1 messages · Page 197 of 1

south siren
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Just replace x by -x

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Same thing to prove (f(x) - f(-x))/2 is odd

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And now you got two functions, one even and one odd, and their sum is f(x)

gusty plank
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ah i see i get it now

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thank you

south siren
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U welcome

gusty plank
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glacial garden
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hey can someone help explain pls
lim x+sin2x / tan3x
x -> 0

prime lynx
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h?

trim lichen
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did you mean x -> 0? @glacial garden

glacial garden
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Oh yeah sorry!!

fleet bear
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I'd try small angle approximations

trim lichen
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so $\lim_{x \to 0} \frac{x + \sin(2x)}{\tan(3x)}$ is what you've got then yes?

solid kilnBOT
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ann.in.a.teacup

glacial garden
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yes!!

trim lichen
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ok do you have any progress on this so far?

glacial garden
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i did earlier but its somewhere in my notebook of attempted calc problem scribbles lol

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i thought i had an idea but can u walk me through it?

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wraith hinge
buoyant void
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@glacial garden Has your question been resolved?

jagged escarp
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cerulean quail
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1.11b?

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cerulean quail
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iron orbit
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need help finding second derivative of y'=(2x-y^2)/(y^3+2xy)

iron orbit
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this is what I got it to using the quotient rule however the book says y'' is (2-y'(3y^2y'+2xy'+4y)/(y^3+2xy)

clear cloud
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Second derivative wrt what

iron orbit
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Trying to figure out how the book got the 2nd derivative compared to using the quotient rule on y'

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@iron orbit Has your question been resolved?

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@iron orbit Has your question been resolved?

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@iron orbit Has your question been resolved?

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@iron orbit Has your question been resolved?

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gritty hollow
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I'm getting the hang of completing the square, but this problem is confusing me. How do I convert this when a and b do not have any common factors outside of 1?

bright quarry
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did you start by dividing by 2?

gritty hollow
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I thought you start by moving the 6 to the other side, but that would also make the other side negative (which would lead to an imaginary number).

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If we divide by 2, does that turn it into 2(x^2+3.5x+3)?

bright quarry
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what?

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usually we have the coefficient of a expressed in vertex form but apparently they don’t want that, also i see no reason why you should move the constant term to the other side

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it’s useless

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this is how you should do it

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first they divide by 2 to get
x^2 + 7/2 x + 3 = 0

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then we observe that (x + 7/4)^2 contains the first two terms x^2 + 7/2 x but the constant term is different

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(x + 7/4)^2 = x^2 + 7/2 x + 49/16

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but we have a + 3

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not a 49/16

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notice that 49/16 = 48/16 + 1/16

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which is 3 + 1/16

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hence (x + 7/4)^2 = x^2 + 7/2 x + 3 + 1/16

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and look

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we have exactly what we had in our original expression but there’s the 1/16 on that side

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so just subtract it from both sides

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and we get
x^2 + 7/2 x + 3 = (x + 7/4)^2 - 1/16

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@gritty hollow do you understand

gritty hollow
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I'm trying to absorb all of this.

bright quarry
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i can give another example if you’d like

gritty hollow
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Can we go step by step?

bright quarry
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sure

gritty hollow
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I get the first part where you divide by 2 on both sides.

bright quarry
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mhm

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would you like another example first?

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maybe the fractions make it more confusing

gritty hollow
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I understand how to complete the square normally. Just not when a does not equal 1.

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I think an easier example where a does not equal one would be good.

bright quarry
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ok

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i think it would be good if you learned how to rewrite an expression instead of it being an equation where we can just ignore the coefficient of a by dividing by it

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so

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$2x^2 + 10x + 25$

solid kilnBOT
bright quarry
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btw, have you seen vertex form? namely
a(x - h)^2 + k

gritty hollow
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I've seen that before.

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So here, we can see that the 2 and the 10 are divisible by 2.

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And that the square root of 25 is 10/2.

bright quarry
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well

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the first step is to always factor out the a term

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so let me walk you through this one

gritty hollow
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Yeah, so we can do 2x(x+5)+25.

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Oh, okay.

bright quarry
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,,\begin{align*}
2x^2 + 10x + 25 &= 2\left(x^2 + 5x + \frac{25}{2}\right)\
&= 2\left(x^2 + 5x + \frac{25}{4} - \frac{25}{4} + \frac{25}{2}\right)\
&= 2\left(x + \frac{5}{2}\right)^2 - 2\left(\frac{25}{4} - \frac{25}{2}\right)\
&= 2\left(x + \frac{5}{2}\right)^2 - \frac{25}{2} + 25\
&= 2\left(x + \frac{5}{2}\right)^2 + \frac{25}{2}
\end{align*}

solid kilnBOT
bright quarry
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if you have a question about any of the steps just ask

gritty hollow
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I can kind of see it? Can you explain the 25/4-25/4+25/2 stuff? The x^2+5 stuff seems relatively straightforward.

bright quarry
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so do you agree that adding 0 to an expression does not change anything

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a + 0 = a

gritty hollow
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Yeah, I agree.

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So it's just 0+25/2.

bright quarry
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so i did that because i wanted to have a + 25/4

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because (x + 5/2)^2 = x^2 + 5x + 25/4

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so to "complete the square" i rewrote my expression to contain a + 25/4

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so i could rewrite it as a perfect square

gritty hollow
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I think I get it now. So it's like a puzzle, in a way.

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All you're doing is making it so that we can factor it neatly.

bright quarry
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yes exactly

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so let’s try to do the same thing in your example

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2x^2 + 7x + 6

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let’s forget about the zero for now

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it’s good practice to be able to keep the factor of 2

bright quarry
gritty hollow
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Okay, so we factor out the 2 and then focus on the parenthesis.

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So we get 2(x^2+3.5x+3)

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Now we have to get b/2.

bright quarry
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$2\left(x^2 + \frac{7}{2}x + 3\right)$

solid kilnBOT
bright quarry
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mhm

gritty hollow
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Which b/2 would be 7/4, which is where that comes from.

bright quarry
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yes

gritty hollow
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Now we have to make c = 7/4^2.

bright quarry
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mhm

gritty hollow
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That would be 49/16.

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Now, 3 = 48/16, so we need to find a way to add 1/16 to it.

bright quarry
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yep

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or you could add zero

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  • 49/16 - 49/16
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then just do -49/16 + 3

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i did it that way because i just saw i could break up 3 like that

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but that really amounted to subtracting 49/16 from 3

gritty hollow
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This means that the other side is -49/16?

bright quarry
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$2\left(x^2 + \frac{7}{2}x + \frac{49}{16} - \frac{49}{16} + 3\right)$

solid kilnBOT
bright quarry
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only do that if they force you to

bright quarry
gritty hollow
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I also have to go soon, but I understand this better now.

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Thank you for all of this.

bright quarry
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you’re welcome

gritty hollow
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I'll close it now, but don't worry. I think I can figure this out now.

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;close

bright quarry
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ok

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have a good one

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good luck

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!done

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gritty hollow
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wicked quail
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Hi

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wicked quail
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Can someone explain me this line please?

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How did h multiply with the denominator

lament reef
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do you mean the second line?

wicked quail
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Yeah

lament reef
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they multiplied the numerator and denominator both by (h+7)

wicked quail
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Oh wait I'm dumb

lament reef
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oop

wicked quail
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bold stream
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does anyone know how to get g(z)? i dont really understand how to get it

unique minnow
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For a fixed z (imagine a plane parallel to the xy plane at that height), what is the area of the square cross-section of the pyramid?

bold stream
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idk im not sure

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are you talking about just the base of the pyramid like 4x4?

unique minnow
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Well if you fix z=0 then the area of the cross section on the pyramid is 16, yes

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But in general, think of a fixed z like that plane I drew. You can think of your integral as "scanning" from the base to the tip of the pyramid, adding up the area of tiny slices of it.

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g(z) should be the area of those slices

bold stream
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oh i see

unique minnow
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In reality, you only need to know x in order to find the area, since the cross-sections are squares centered at the origin

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So if for a fixed z you can find the corresponding x value, that should give you insight as to what the area of the cross-section is

bold stream
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oh i see what you mean thank you

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but im still just not sure how to actually get g(z). given z = h(x-2)^2/4

unique minnow
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Let's say z = 1.
From the equation you're given, can you find the x-value for the location of the cross section?

bold stream
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yeah

unique minnow
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To do that you solved for x in the equation 1 = h(x-2)^2/4

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Once you have that value, double it and you should get the side length of the square yes?

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Now, if z isn't given, what if you try to solve for x in terms of z?

bold stream
unique minnow
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The squares are centered about the z axis.
If you find the value of x for a fixed z, that's really just where the red line touches the square cross section.

bold stream
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oh i think i see i

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it

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but then i would have to square the whole thing after too right?

unique minnow
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Yeah

bold stream
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(2(-sqrt(4z/h)+2))^2
I just dont get why we need the square and - now

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apparently thats the answer

unique minnow
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From the equation you have, you get

$$(x-2)^2 = \frac{4z}{h}.$$

Technically, this yields $$x-2 = \pm \sqrt{\frac{4z}{h}}$$

Now, since $x \le 2$, we must have $x-2 \le 0$, so you need to just keep the negative root.

This gives you $x = -\sqrt{\frac{4z}{h}} + 2$
Then you double that to get the side length of the cross section, and square it to get the area of the cross section.

solid kilnBOT
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Azyrashacorki

bold stream
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oh i see now but im little confused why x must be less than or equal to 2

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is it cuz im not seeing where the axis are rn

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im kinda confused where they are located rn

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oh nvm i think i got it

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thank you

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sullen remnant
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Good morning all, how do I solve 9(3x+4)-2x=11+5(4x-1)

trim lichen
sullen remnant
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27x + 4 - 2x = 11 + 20x -1

trim lichen
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9(3x+4) is not equal to 27x+4

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you need to distribute properly

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and likewise for the other bracket, where you made the exact same mistake a second time

sullen remnant
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ok

trim lichen
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can you tell me what 9(3x+4) properly expands to?

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also btw you have the "ask pronouns" role -- what are your pronouns?

sullen remnant
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My answer is -6

sullen remnant
trim lichen
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can you show all your work leading up to the answer?

sullen remnant
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27x +36 - 2x = 11+ 20x -5

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then you group like terms
27x -20x -2x = 11+5+36

trim lichen
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sign error at least once

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twice actually

sullen remnant
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then you divide both sides by 5

trim lichen
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11 - 5 - 36 on the right

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not 11 + 5 + 36

sullen remnant
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no no the letter x not multiplication

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Oh yes minus

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it escaped me

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i actually used a minus in my book

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so instead 27x -20x - 2x = 11-5-36

trim lichen
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yes

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ok good

sullen remnant
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Ok

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thank you for your service.

trim lichen
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.

sullen remnant
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right

trim lichen
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that wasn't me reminding you to put a period

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that was me conveying a bit of shock at the word "service"

sullen remnant
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do not be shocked

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@sullen remnant Has your question been resolved?

sullen remnant
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Yes, it was.

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@sullen remnant Has your question been resolved?

sullen remnant
#

Yes

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fringe valve
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can anyone help me explain what this is

trim joltBOT
trim lichen
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some kind of strange little graph

fringe valve
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it's from a set of numbers

trim lichen
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thats all well and good but you have not given us any context

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and expect us to somehow intuit something from this graph alone with zero context

fringe valve
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the numbers arent actually from a math problem, i was actually trying to categorize genes based on if it had the phenotype, genotype or none. 7 different types of genes all combinations. i decided to add colors to make it easier and so that the colors would make sence i gave each color a number. these numbers seemed to have a weird type of pattern to it so i plotted them in python and got this

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do you want me to send the full dataset?

fringe valve
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i need help finding a formula or a program that can put out the same numbers

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i made something in python but it's limited to the first 3^8 numbers

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if i want anything higher i would have to add another 2 lines

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i'm curious if anyone here could help me find a better way of prediciting the numbers

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and what these numbers are

umbral knot
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Perhaps use a for loop and use index as an exponent? I have never used pylab before

fringe valve
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do you maybe know what this numberset is?

umbral knot
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Thank you

umbral knot
fringe valve
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it seems to be repeating

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it seems to be divided in thirds

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i have a theory this is some result of base 3 or something

jaunty silo
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Don't you alreay have a code that generates the number you want?

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you want to calculate it without using loops&ifs?

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Sorry I missed a point

fringe valve
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but yeah the problem is that im basically brute forcing it

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i have to add more lines to generate higher numbers

jaunty silo
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If you only have problems with not want to add more lines

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while i<=b:
    x1.append(i)
    y1.append(y)
    for j in range(math.ceil(math.log(i,3)),-1,-1):
        if (i+1)%(3**j)==0:
            y += 1-2*j
            break
    i +=1
fringe valve
jaunty silo
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oh add import math on top of the code

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or below from pylab import * it doesn't really matter where the line is

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as long as it is on before the while loop

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you get error?

jaunty silo
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from pylab import *
import math
a = 0
b =100000
x1 = []
y1 = []
y=0 
i=0
while i<=b:
    x1.append(i)
    y1.append(y)
    for j in range(math.ceil(math.log(i+1,3)),-1,-1):
        if (i+1)%(3**j)==0:
            y += 1-2*j
            break
    i +=1


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like this

fringe valve
jaunty silo
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And by the way sorry for my mistake again, there's some error to be fixed. Please change for loop as

for j in range(math.ceil(math.log(i+1,3)),-1,-1):

I forgot adding 1 to i

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I keep forget log is not defined on 0

fringe valve
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what should i define it as??

jaunty silo
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So overall code woulde be like

from pylab import *
import math
a = 0
b =100000
x1 = []
y1 = []
y=0 
i=0
while i<=b:
    x1.append(i)
    y1.append(y)
    for j in range(math.ceil(math.log(i+1,3)),-1,-1):
        if (i+1)%(3**j)==0:
            y += 1-2*j
            break
    i +=1

plot(x1, y1,'-')
show()
    
fringe valve
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oh my god thank you

jaunty silo
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I hope this help

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good luck on whatever you doing

fringe valve
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do you maybe know anything of this pattern?

jaunty silo
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I'm trying to analyze the data, but nothing remarkable yet found for me

fringe valve
jaunty silo
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I don't know if this would mean anything important, But they seems to be bounded between $log_{\sqrt{3}}(x)$ and 1

solid kilnBOT
#

Dri111

fringe valve
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hold on let me send you the original chart of numbers, i think it has something to do with base 3

jaunty silo
#

oke

exotic tundra
fringe valve
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i didn't really know it was base 3 before i looked twice, it was originally meant as a system for deciding the color of squares catwhy

jaunty silo
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is the number generated with computer? or is this some kinds of experiment result?

fringe valve
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it's a thought experiment you need a pc for

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you have 7 pairs of chromosomes, aa bb cc dd ee ff and gg.

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but it can also be aA bB cC dD eE fF and gG

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and aa bb cc DD ee ff gG

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and all the other thousands of combinations

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if it has no large letters trait is non existent and it's a 0

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if a pair has 1 large letter its a genotype and given a 1

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and if a pair has both it's a phenotype and get's 2

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so base 3

jaunty silo
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so each digit is each pair of chromosome?

fringe valve
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yes

jaunty silo
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then why are there 8 digit?

fringe valve
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0 is small letter small letter

fringe valve
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it was meant as a little biology presentation on how traits can reapear

jaunty silo
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and what about 6, 8 and those that are not available in base-3?

fringe valve
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aa is 0 aA is 1 and AA is 2

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8 pairs

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there are 3 variants of each pair

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8 pairs

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you get base 3

jaunty silo
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so for example 7 means there are total 7 large chromosome in 7 chromosome pair?

fringe valve
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it wasn't meant to predict anything

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i asigned a color to make the chart more organized

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let me just send the entire thing to you

jaunty silo
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Then for example how should I intepret number 8 in the numbers?

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oke

fringe valve
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it means that 8 chromosomes in the 8 pairs are large

jaunty silo
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ahhhh

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now I cleary see what you mean

fringe valve
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ye sorry im bad at explaining

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😅

jaunty silo
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no no it was just lack of background for me

fringe valve
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Oh ok 😅

jaunty silo
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I can't find any specific more works, this is my best

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this is cumulative form of the data you have

fringe valve
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thank you

#

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half marsh
#

Can someone look at my proof?

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covert spindle
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@half marsh Has your question been resolved?

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@half marsh Has your question been resolved?

half marsh
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<@&286206848099549185>

half marsh
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.close

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round thorn
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round thorn
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no

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nvm i got it .close

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.close

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wraith hinge
#

Hello I have a clash of clans question

trim joltBOT
#

Please don't occupy multiple help channels.

wraith hinge
#

Basically: I have 5 builders that do upgrades on structures.

The question is to figure out whether the Book of Spells or the Book of Building saves a greater total amount of days when you use it.

odd snow
#

This channel is for math bro

wraith hinge
odd snow
#

You opened two channels

wraith hinge
#

Ohh sorry

odd snow
wraith hinge
odd snow
#

Because the book of spells upgrades spells when you are upgrading them and the book of building is better for building

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Correct

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Which leaves you 1 builder to get it to do something else

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All in all usually what is the most time efficient is to have all your builders busy at all times

wraith hinge
#

Basically my question is, if you have 5 builders and use a book of building on a 10-day upgrade: does it save in total 10/5 =2 days?

Compared to the Book of Spells: since in the laboratory you can only do 1 upgrade at a time (as opposed to 5 upgrades simultaneously on buildings using the 5 builders), then the Book of Spells saves exactly the amount of days that is equal to how long the upgrade is

wraith hinge
#

But I feel like I am missing smth

odd snow
#

so you can actually do both

wraith hinge
#

Like, if you use a Book on a 14-day long upgrade, then you literally do not have to spend 14 days doing it

#

So how is it 14/5

odd snow
#

What town hall are you

wraith hinge
#

I am purely interested in the math of this

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I don’t rly have any books rn

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I have been debating which book is better

odd snow
#

I'd say building

wraith hinge
#

I give this math but feel like I am missing smth

wraith hinge
#

Cause spells saves 14 days if the upgrade is 14 days

odd snow
#

because you can still use your troops while upgrading them

#

It saves you more time too

wraith hinge
#

But Book of Building saves 14/5 why is it so

odd snow
#

Well you can only use 1 book

wraith hinge
#

Haha I mean you can use any amount of books

#

I’m rly curious if someone can tell me what I’m missing haha

sturdy skiff
#

Bro clash of clans is not that serious 🙏 💔

wraith hinge
sturdy skiff
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@wraith hinge Has your question been resolved?

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fluid skiff
#

help in integrating 1/r^2 dr

trim joltBOT
fluid skiff
#

1/r^2 can be written a r^-2

#

Power rule

#

(r^-2+1 /-2 +1) + C

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r^-1 /-1

#

my problems is

#

r^-1 / -1 = 1/r^-1

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How did we get rid of the sign -

verbal stream
#

I think there should be a negative sign

#

-1/r

verbal stream
fluid skiff
#

that the problem im facing

verbal stream
#

$\frac{r^{-1}}{-1} = -r^{-1} = -\frac{1}{r}$

solid kilnBOT
fluid skiff
#

but im confused is there a property that states
-1 = 1/1?

verbal stream
#

?

fluid skiff
#

i know that the is true for the exponent only

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x^-1 = 1/x

verbal stream
#

no -1 is not 1/1 lol

fluid skiff
#

alright thanks for the help

#

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wraith hinge
#

my teacher said if i cant get this right i fail

wraith hinge
#

Please help

zinc ginkgo
#

Sounds cruel

wraith hinge
#

please

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i need to pass

bold rapids
wraith hinge
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please

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im at a 11%

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@wraith hinge foucus

#

helpp

bold rapids
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11?!?

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yes you need to focus

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uhh gimmie a second

#

but in the mean while

#

<@&286206848099549185>

wraith hinge
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yay

#

<@&286206848099549185>

#

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wraith hinge
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wraith hinge
#

Got kernel(L)={(0,0,0)}

#

so basis would also be (0,0,0)

ionic pendant
#

a basis for {0} is not {0} because it is not linearly independent

wraith hinge
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and basis for Range(L) as {(1,1,0),(-1,2,0),(0,0,1)}

wraith hinge
#

so i need 3 vectors

ionic pendant
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by convention a basis for the vector space {0} is taken to be the empty set

wraith hinge
#

okay

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for part d

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one min

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i will send my proof

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this works ?

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so for L to be one to one i have to show that if T(v_1)=T(v_2) then v_1 = v_2

#

cloud ?

ionic pendant
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sure

wraith hinge
#

and for onto

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So

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For onto

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I have to show this equation has a unique solution for every x1,y1,z1

#

?

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Oh wait wrong matrix

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There

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Is this also right?

wraith hinge
#

Rank (A) = Rank(Augmented matrix)

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Correct ?

wintry stag
#

An onto function doesn't require a unique element in the preimage

#

The way that question is phrased doesn't make me think they want you to prove it rather than just give a yes or no answer with a brief justification.

#

Like for 1-1, you have that Ax = Ay and you've already shown that A has rank 3, so x = y without the formality.

wraith hinge
wintry stag
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and if you don't have access to the existence of a matrix representation of the LT, then you shouldn't be writing that in the form of an augmented matrix

wraith hinge
#

So Proving det(A) not equal to 0 would be sufficient ?

amber python
#

you've already shown that range(L) = R^3

wraith hinge
#

I did?

amber python
wintry stag
#

I assumed that when I said you could have wrote a couple sentences to justify your answer but then you said you wanted to prove it, that this meant that you wanted to show it using the definitions of 1-1 and onto, by explicitly showing that for any y in the image there exists an x in the preimage such that L(x) = y

wraith hinge
# amber python

If I just show that those 3 vectors are independent my work is done

amber python
#

well you claim they are a basis

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if they were not linearly independent, then your claim that they are a basis is wrong

wraith hinge
#

Oh yeah lol

amber python
#

also for 1-1, ker(L) = {0} is all you need

#

which you also stated as part of your answer to b

wraith hinge
#

They did say this

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But I thought the converse isn't always true

wraith hinge
#

Inwill do it

wintry stag
#

You don't -have- to do anything, it's just not clear what you are trying to practice

amber python
#

your answers to parts b and c should instantly tell you the answers to parts d and e

trim lichen
wraith hinge
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converse would be "ker(L)={0_v} implies LT T:V -->W is one to one"

#

damn

amber python
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there is no converse to this statement

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it is not an implication

wraith hinge
#

but

trim lichen
wraith hinge
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say i have the statement "A set V is considered a vector space if and only if V contains 0"

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its converse would be "If V contains 0 then V is a vector space"

trim lichen
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no

wraith hinge
#

but this isnt true always right

trim lichen
#

but our point is a statement of the form A <=> B doesn't have a converse at all

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do you understand that A <=> B is a different kind of beast than a one way implication?

wraith hinge
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nope

#

e

trim lichen
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A <=> B means "A implies B, and B implies A"

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it is a two-way implication

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do you understand this?

wraith hinge
#

yes

ionic pendant
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so A => B and B => A are converses of each other on their own

wraith hinge
#

so "if and only if" is a two-way implication ?

trim lichen
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yes

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that is what ive been saying all along

wraith hinge
#

okay so ker(L)={0_v} means L is one to one

#

and for onto

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🙏

#

i will do it later

#

thanks everyone

#

.close

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keen cliff
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keen cliff
#

calculus how do i use the integral(ax+b)^n formula properly here

#

just the equatio nthat comes after b.

trim lichen
keen cliff
#

oh

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is there a shortcut to this kind of question then

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or do i always have to just expand it out then integrate

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im just kinda lazy

quick tusk
#

gotta expand

trim lichen
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there's not really any sense of "always"

quick tusk
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or use hyperbolics, but i doubt that makes it much easier

trim lichen
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but for this one yes you have to expand. it is not that bad here

quick tusk
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yeah you would still have to reduce the power

keen cliff
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hmm

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okay

#

i understand this then

#

thank u guys sm for your help

#

🙏 🙂‍↕️

quick tusk
quick tusk
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keen cliff
#

.close

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pulsar mulch
#

Prove that the vectors v₁, v₂, ..., vₖ are linearly dependant if and only if there exists real numbers λ₁, λ₂, ..., λₖ that arent all zero such that
v₁λ₁ + v₂λ₂ + ... + vₖλₖ = 0.

frozen plover
pulsar mulch
#

1 sec

main sigil
#

Did you mean arent all zero

frozen plover
#

also what's your definition of linear independence

pulsar mulch
#

bear with me guys im tryna translate the textbook from swedish to english, my bad 😭

main sigil
pulsar mulch
#

yes this is derived from that:)

pulsar mulch
#

Sorry for the confusion, thats right

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This probably isnt very difficult I'm just struggling with drawing conclusions from the proof that's in my textbook (and wikipedia, ill attach it) so that I can actually somewhat understand it

main sigil
#

And used that to express one of the vs as linear combination of the others

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Thus showing its linearly dependent

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E.g. 2 * [1, 2] + (-1) * [2, 4] = 0
And we can rearrange this to get
[1, 2] = 1/2 [2, 4]

#

And this shows that its linearly dependent

#

And we can do the opposite similarly

pulsar mulch
#

extending off of that, could you interpret all lambda = 0 as a non-real combination of vectors, proving that it is infact linearly independant?

#

i.e. given a sequence of vectors that are linearly independant, the only way to create a combination is to divide by zero which is undefined

main sigil
main sigil
#

Its linearly independent because if it was linearly dependent, then we would have v1 = some linear combination of other vs and we could rearrange that to get a non-zero solution for the equation we started with

pulsar mulch
#

I understand

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This really was not that complicated after all, think i just needed a human to talk to about it

#

Thank you a lot for the help 🙏

#

.close

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wind venture
#

Hi, I got stuck when trying to check if my Method of Moments Estimator is unbiased. So I have done the following. \
\
Gamma Distribution is defined as
\begin{align}
f(x) = \frac{x^{\alpha - 1} e^{-x/\beta}}{\beta^\alpha \Gamma(\alpha)} \quad \text{for } x > 0
\end{align}
\
Let $x_1, \ldots, x_n$ be an i.i.d sample with $\gamma(\alpha, \beta)$ distribution. \
\
The gamma's moment-generating function is
\begin{align}
M(t) = E[e^{Xt}] &= \int_{0}^{\infty} e^{xt} \frac{x^{\alpha - 1} \exp\left( -\frac{x}{\beta} \right)}{\beta^\alpha \Gamma(\alpha)} \dd{x} = \frac{1}{(1 - t\beta)^{\alpha}}
\end{align}
\
In such way, the first moment and second moment is
\begin{align}
{\dv{M}{t}}(0) &= \frac{\alpha\beta}{(1 - t\beta)^{\alpha + 1}} \Bigg|{t = 0} = \alpha\beta \
{\dv[2]{M}{t}}(0) &= \frac{(\alpha^2 + \alpha)\beta^2}{(1 - t\beta)^{\alpha + 2}} \Bigg|
{t = 0} = (\alpha^2 + \alpha)\beta^2
\end{align}
\
So, the expectation and variance of gamma is
\begin{align}
E[\gamma(\alpha, \beta)] &= \alpha\beta \
V[\gamma(\alpha, \beta)] &= (\alpha^2 + \alpha)\beta^2 - (\alpha\beta)^2 = \alpha\beta^2
\end{align}
\
We got the following system
\begin{align}
E[\gamma(\alpha, \beta)] = \sum_{i = 1}^n \frac{x_i}{n} &\iff \alpha\beta = \sum_{i = 1}^n \frac{x_i}{n} \
E[(\gamma(\alpha, \beta))^2] = \sum_{i = 1}^n \frac{x_i^2}{n} &\iff(\alpha^2 + \alpha) \beta^2 = \sum_{i = 1}^n \frac{x_i^2}{n}
\end{align}
\
Now.. solving the following system for $\alpha$ and $\beta$
\begin{align}
\hat{\alpha} &= \frac{\overline{X}^2}{V^2} \quad \text{Note that } \overline{X} = \sum_{i = 1}^n \frac{x_i}{n} \
\hat{\beta} &= \frac{V^2}{\overline{X}} \quad \text{and also } V^2 = \sum_{i = 1}^n \frac{x_i^2}{n} - \left( \sum_{i = 1}^n \frac{x_i}{n} \right)^2
\end{align}
\
Once done all of that, I should show if $E[\hat{\alpha}] = \alpha$ but not sure how to process with $E\left[ \overline{X}^2 / V^2\right]$

solid kilnBOT
#

A.L.I.C.E

trim joltBOT
#

@wind venture Has your question been resolved?

trim joltBOT
#

@wind venture Has your question been resolved?

wind venture
slate aspen
#

Wait, give me a second to brush up my MoM theory

wind venture
#

Yaaaay eeveekawaii

slate aspen
#

Aaah it is just your last step I think? So you want to show now $E[\alpha] = E[\frac{X^2}{V^2}] = \alpha$, is that correct?

solid kilnBOT
#

Mathemagician

wind venture
#

Yes I got stuck because of that /V^2

slate aspen
#

just use the proporty of Expectations that says: $E[X/Y] = E[X]/E[Y]$

solid kilnBOT
#

Mathemagician

wind venture
#

: O

#

Lemme check

#

Btw, $E[\overline{X}^2] = E[\overline{X}]^2$, that is true, right?

solid kilnBOT
#

A.L.I.C.E

slate aspen
#

Yes, since $\bar{X}$ is just a constant, it is correct (but this is not in general true)

solid kilnBOT
#

Mathemagician

slate aspen
#

Can it be that your Variance should be $V^2 = \alpha \cdot \beta^2$ instead of just $V$? Otherwise, it will not work, I think the notation should be $V^2$, no?

solid kilnBOT
#

Mathemagician

wind venture
#

Hmm, how so by instead of just V? I've written it as V^2, right?

slate aspen
#

Yes but you say in equation 6: $V = \alpha \cdot \beta^2$, but later in equations 9 and 10, you use $V^2$ instead of $V$, right? That is what might give problems in the calculation

solid kilnBOT
#

Mathemagician

wind venture
#

Ahhh sorry, I meant like V[X] of gamma instead of V^2 of the sample

slate aspen
#

No probs 🙂 But then the problem is solved and you can show the unbiasedness right? Or are you still stuck?

wind venture
#

I'm trying to compute E[V^2], I used to do it turning it into chi-squared

#

That usually works with normal distributions XD

slate aspen
#

but why do you need E[V^2]? I think it should be E[V], no?

wind venture
#

Hmm, you mean like $E[\overline{X}^2 / V^2] = E[\overline{X}^2]/E[V^2] = E[\overline{X}]^2 / E[V]^2$

solid kilnBOT
#

A.L.I.C.E

slate aspen
#

I think there shouldn't be a V^2 in the first expectation in the first place

wind venture
#

I got lost sadcat

slate aspen
#

It's ok

#

so

#

in equation 6, you calculate V not V^2, right?

wind venture
#

I computed sigma^2 in there

slate aspen
#

yesss

#

but V = sigma^2, right?

wind venture
#

Hmm, it should not be V^2 = sigma^2, should it?

slate aspen
#

no exactly!

#

It should just be V

#

and therefore, it should also just be $E[X^2/V]$ instead of $E[X^2/V^2]$

solid kilnBOT
#

Mathemagician

wind venture
#

Hmmmmmmmmm I see, so technically I can do like this $E[\overline{X}^2/V] = E[\overline{X}]^2 / E[V] = (\alpha\beta)^2 / (\alpha\beta^2) = \alpha$

solid kilnBOT
#

A.L.I.C.E

slate aspen
#

yess! Indeed! thats the way to go girl

wind venture
#

I thought that I was not allowed to change it like that

#

I mean, it feels like cheating XD

slate aspen
#

but you don't change anything, you started with V and you finish with V, you never introduced V^2, so you should not use V^2 :))

wind venture
#

Yeah, thanks for the help !

slate aspen
#

No probs, good luck!!

wind venture
#

: D

#

, thanks

#

,thanks

#

Hmm

#

,close

#

.thanks

#

.close

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#
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plain tusk
#

quick help

trim joltBOT
red mountain
#

whats your question

plain tusk
#

ive only seen questions like this

#

without the other number being squared

#

so im kinda confused

indigo ferry
#

You need to factor that?

red mountain
#

try factoring

#

into (ax-by)(cx-dy)

plain tusk
plain tusk
indigo ferry
#

Write $-17xy = a + b$ such that $ab = (3x^2)\cdot (20y^2)$

solid kilnBOT
#

casework

plain tusk
#

ahh ok

#

yeah i see now

#

thanks for the help

#

.close

trim joltBOT
#
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sour tulip
#

This is the answer for exercise 3 I just need someone to explain polar coordinates and what exactly happened in the second diagram, it looks like the velocoty is dicided into perpendicular components but why does the writer call them axes? Also toward the bottom of the page when velocity component is described is it a typo when they write r again besode r dot and theta beside theta dot(dot is the time derivative notation)

crimson pulsar
#

Magical Math Escape Game

Objective: Discover which magician managed to rob a bank without leaving any trace by solving math problems.

The Suspects
(x+2)(x+4)

(x-2)(x+4)

(2x-2)(x-4)

(5x+7)

(3x+6)(2x+4)

Names and Expressions of the Suspects:
Lionel Séchal: 6x² - 2x - 8

Agée L'Witch: 2x² + 22x + 24

Luke: 2x² + 2x - 8

Rachel Atlas: 2x² - 10x + 8

Merritt Lockline: 3x² + 18x + 24

Thaddeus Bigallet: 25x² + 70x + 49

Magic Program 1:
Choose the number (-4)

Square it

Subtract 7

Divide by 2

Add 5

Magic Program 2:
Choose the number x

Add 7

Multiply by 2

Add the initial number

Execute this Scratch program with (-3), then with the letter x:
when [green flag] clicked

ask [Choose a number] and wait

set [my variable] to [answer]

add [7] to [my variable]

set [my variable] to [my variable] * [2]

set [my variable] to [my variable] + [answer]

say [my variable] for [2] seconds

Magical Items and their Associated Numbers/Expressions:
Crystal ball: 7

Magic wand: 12

Potion: 3x + 14

Hat: 2x + 13

Magic book: 5

#

pls help

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@sour tulip Has your question been resolved?

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tribal marten
#

.

trim joltBOT
tribal marten
#

How to solve thisss

#

,rotate

solid kilnBOT
tribal marten
#

Idk howw

young forge
#

Ohh

#

The formula is just r(theta)

#

That’s it

#

U multiply your radius with your angle in radians

tribal marten
#

Hmm?

#

R(theta)?

young forge
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The angle of your arc length right

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It’s 30

#

U convert it into radians

#

Then you just multiply it with your radius

young forge
trim joltBOT
#

@tribal marten Has your question been resolved?

tribal marten
#

I still don't get itt😭😭

tribal marten
young forge
#

You know radians right?

tribal marten
#

Yel

young forge
#

Ok so you just multiply your ridians with your angle in radian

#

Lemme do it

tribal marten
#

Okay

young forge
tribal marten
#

Ohhhhh

young forge
#

Right

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That’s it^^

tribal marten
#

Waittt

#

Where did 5 come from againn

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Thats 15?

young forge
#

Oh it’s because when you multiply 15 with 1/6

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It becomes 15/6

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U simplify the fraction

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It becomes 5/2

tribal marten
#

Ohhhhhhhh

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Okay thank youuuuuuu

#

Lasttt

young forge
#

Yesss👍

tribal marten
#

15 is the given Cm?

#

And 30 is whats left from 330 degree?

young forge
young forge
tribal marten
#

Can you make a problem ill try to solve real quickk

young forge
#

Sure

tribal marten
#

5/4?

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5 over 4?

#

Pie

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5/4 π?

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Am i correct? @young forge

young forge
#

Yess

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Correct 👍

tribal marten
#

Thank you

#

Can i ask another stuff

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Waitt

young forge
#

Sure

tribal marten
#

,rotate

solid kilnBOT
#

Couldn't find an attached image in the last 10 messages.

tribal marten
#

/rotate

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,rotate

solid kilnBOT
tribal marten
#

Do you know thiss?

young forge
#

Lemme try first

tribal marten
#

Okiee

young forge
#

Got it

#

U add up everything together then u equate it to 360

tribal marten
#

Yes i knoww

young forge
#

Then?😭

tribal marten
#

But how to find value of X

young forge
#

Ohhh

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U gather all the x on one side and the constants on the other

tribal marten
#

Should i add

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The stuff

tribal marten
young forge
#

Yes all together

tribal marten
#

Then what nextt

young forge
#

Cuz together they add up to 360

young forge
#

And you bring your constants on the RHS

tribal marten
#

😭😭😭

young forge
#

What’s up💀

tribal marten
#

Guess what

#

HAHAHA

young forge
#

Wait I’m Guessing rn

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Processing

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Jk just say it

#

💀

tribal marten
#

Don't get it lol

young forge
#

🧍‍♂️

tribal marten
#

lol

young forge
tribal marten
#

Where did 31 and 465 came fromm

#

Thats the thing i need to know so that i got it

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@young forge

young forge
#

Because I collect all the x together

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And all the other terms together

tribal marten
#

You combined all X?

young forge
#

Yes

#

-55 - 50 =-105 then I bring to the other side become 360+105=465

tribal marten
#

Ohhhh

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Okay

#

I got itttt

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Thank youuu sooooo muchhh

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Really appreciate it:))

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@young forge Thankk you brocatlove

young forge
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No problem🙏

tribal marten
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Goodluck in your lifeee

#

Bye byeee

young forge
#

Okay thank you

#

You too^^

tribal marten
#

,close

#

.close

trim joltBOT
#
Channel closed

Closed by @tribal marten

Use .reopen if this was a mistake.

#
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Show your work, and if possible, explain where you are stuck.
After 15 minutes, feel free to ping <@&286206848099549185>.
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• Be polite and have a nice day!

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turbid tiger
#

in slve a can't we consider domain x>or=4? just like we did in slve b?

turbid tiger
#

<@&286206848099549185>

worthy eagle
#

!15m

trim joltBOT
#

Please only use the <@&286206848099549185> ping once if your question has not been answered for 15 minutes. Please do not ping or DM individual users about your question.

simple haven
#

@turbid tiger if you have x = -5 then the expression in part a is still defined.

#

the reason for the restricted domain in part b is due to the sqrt, you can't take the square root of a negative number.

turbid tiger
#

i exactly understood .

#

thanks @simple haven

#

.close

trim joltBOT
#
Channel closed

Closed by @turbid tiger

Use .reopen if this was a mistake.

trim joltBOT
#
Available help channel!

Send your question here to claim the channel.

Remember:
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!

Read #❓how-to-get-help for further information on how to ask a good question, and about conduct in the question channels.

proper saffron
trim joltBOT
proper saffron
#

idk how to solve this

#

do you use law of sines or cosines

#

and how do you use them do you jst plug x and y?

trim joltBOT
#

@proper saffron Has your question been resolved?

indigo ferry
#

As x + y = y + x

violet gust
#

You dont need sine rule or anything here. A simple angle chase would get you the answer

#

Assume one of the angles, say A, to be some value.
Then you can work from that and find the angle at C in terms of the angle at A

proper saffron
indigo ferry
#

$$|AC| = |BC|$$

solid kilnBOT
#

casework

proper saffron
proper saffron
violet gust
proper saffron
#

so it would be 2a+b=180?

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because bottom angles are the same right?

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its an icosloes

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triangle

violet gust
#

yea, 2A+C = 180

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according to the conventional notations

proper saffron
#

and then a+c=90

violet gust
proper saffron
#

wait

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a+c/2=90

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you divide whole thing by 2

violet gust
#

yea, but that doesnt seem to help at anything does it?

proper saffron
#

yeah

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makes it more complicated

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ok but what do you do after 2a+c

violet gust
#

use some properties of triangles you know

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congruence, exterior angles, ...

proper saffron
violet gust
#

Hint if you want: ||calculate the angle KLB||

proper saffron
#

wait also the line in the middle doesnt do anything right?

indigo ferry
#

You have like a million isosceles triangles. If you just use every single one of them. You have what you need

proper saffron
#

hold on

proper saffron
#

blc is 180

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so divide that by 2

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and then both angles are 90

violet gust
proper saffron
#

idk what its called

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supplementary or smt

violet gust
#

Pretty sure thats called wrong

proper saffron
violet gust
#

whyd you say the angles are equal?

indigo ferry
proper saffron
violet gust
#

ngl, it doesnt

proper saffron
#

ok nvm

violet gust
#

and they do say its not to scale

proper saffron
indigo ferry
violet gust
#
  • you should never even assume the figures are correct. They are more of a visual guidelines
proper saffron
#

idk how to continue

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like no clue

violet gust
#

Do you know exterior angles of a triangle?

proper saffron
violet gust
#

Like KLB is an exterior angle of the triangle CLK

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And that triangle is isosceles

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you can try to write the angle KLB in terms of the angle ACB

proper saffron
#

wait

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isnt exterior angle

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like 360-inner angle=exteriour angle?

indigo ferry
#

No

violet gust
indigo ferry
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exterior angle is 180- inner angle

proper saffron
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ok

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i cant

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i need more help

violet gust
proper saffron
#

i dont know how to

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do you use the sidelenghts

violet gust
#

can you show your work? Like show me a diagram you drew and mark the angles A and C on it

proper saffron
#

ok

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kinda did it on paint

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so its a bit messy

violet gust
#

thats fine. I too do that a lot

proper saffron
#

ive just been noting down what we have been talking about

violet gust
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Ok, any other angle you see thats easy to mark?

proper saffron
violet gust
#

yea.

proper saffron
#

or just mark

violet gust
#

I meant mark in the figure in the sense that you can calculate it

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KL = CL means there is one angle that is easy to mark

proper saffron
#

i think that one

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near the l

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OH

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wait

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i think i know

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wait kl is the angle opposite to the one i did rn right?

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and cl is the very top one?

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then i think ik

violet gust
#

KL and CL are the sides

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they have length x

proper saffron
#

oh

violet gust
#

That means CLK is an isosceles triangle

#

So, with that information, what can you say about the other angles in the triangle?

proper saffron
#

in clk

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is also 2b+c=180

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right?

violet gust
#

no...

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why would there be some angle that is same as the angle CBA?

proper saffron
#

wait

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uh

#

the veru top angle

violet gust
#

Like, if you think so, you must provide a reason with each statement you make

proper saffron
#

is the same as

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the acute angle opposite the one i marked rn

violet gust
violet gust
#

YES

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CKL = KCL

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good

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can you now tell me what is the exterior angle KLB equal to?

proper saffron
#

yeah idkk how to name angles

violet gust
#

you can name angles with the three vertices. if the angle is ABC, then the angle is at the vertex B, and formed between the lines AB and BC

proper saffron
#

ok

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so ABL is the angle near corner b

violet gust
#

yes

proper saffron
#

wait holdon

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maybe i know

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how do you do exterior angle

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like KLB+180?

violet gust
proper saffron
#

oh

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180-klc?

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isnt KLC the inner angle

violet gust
#

yea

proper saffron
#

so i got it

#

ok

#

2y+KCL=180

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which means KCL=y/2

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right

violet gust
proper saffron
#

uh

#

i can explain

violet gust
#

wait no scratch that

proper saffron
#

ok

violet gust
#

y is the side

violet gust
proper saffron
violet gust
#

can you rewrite it then? with the correct variable

proper saffron
violet gust
#

whats z? and no, i dont think thats correct

proper saffron
violet gust
#

coz KCL and CKL are the equal angle in this triangle

proper saffron
#

oh true

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2z+KLC=180?

violet gust
#

yea

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thats correct

proper saffron
#

wait no holdon

#

the thingy i did with y/2 is wrong

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im pretty sure

violet gust
#

mhm

proper saffron
#

what do i do next

violet gust
#

We are still at the same step You gotta find the exterior angle KLB

proper saffron
violet gust
#

180-KLC

proper saffron
#

can you give me a hint

#

another one

#

maybe i can figure it out