#help-4

1 messages · Page 58 of 1

marble arch
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With 2

wintry cape
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👍 so how does all of this help me move forward from this

marble arch
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There'd be an (x - 5) multiplied to the 2x

wintry cape
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Alright

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So make another bracket with that?

marble arch
wintry cape
wintry cape
marble arch
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Yes yes, keep it outside

wintry cape
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This

marble arch
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The (x - 5)³

wintry cape
marble arch
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Yes that's correct

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Now simplify 2x(x - 5)

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And evaluate it with -4x²

wintry cape
marble arch
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Yeah that's fine, now you can take -2x common from (-2x² - 10x)

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So you can take it out

wintry cape
marble arch
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Whoops, it'd be +5, we've already taken the minus sign outside

wintry cape
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Silly mistake 😭

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Ok is that the final answer
I think it is

marble arch
wintry cape
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Anything I can write to show how I went from the first part to the second

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I know that I will look back and be confused on how I went from point a to point b

marble arch
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Well, the first step shouldn't be there at all

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The second step should be the first step

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Also if it makes it easier for you, then you can make the (x - 5) inside as (x - 5)¹

wintry cape
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(2x(x-5) - 4x^2(x-5)^3) is the first step

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Then

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Right

marble arch
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Yes, also close the bracket after 4x²

wintry cape
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Wdym

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Isn’t 4x^2 with the (x-5)^3

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As that’s how it was in the problem

marble arch
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Well, you've taken (x - 5)³ common

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Not 4x² too, 4x² remains inside, like that's why we take something common in the first place

wintry cape
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So like that then

marble arch
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No mate, the bracket is after 4x² and before (x - 5)³

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Sorry mate, I gotta go now

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It's getting pretty late here

wintry cape
wintry cape
marble arch
wintry cape
marble arch
wintry cape
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U had a lot of patience today that I don’t have

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😭

marble arch
wintry cape
marble arch
wintry cape
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Fixed my step 1 with the brackets n stuff

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Time for number 19
I should start first by looking for a GCF

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Where I’m at

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First bracket is a sum of two cubes
Second bracket is a difference of two squares

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?

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Can someone let me know if I did this right?

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Number 19

vale dockBOT
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@wintry cape Has your question been resolved?

wintry cape
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<@&286206848099549185> ?

normal hollow
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But did u need to expand the sum of cube and sum of squares?

wintry cape
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Fed up with factoring so don’t mind me

normal hollow
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But do u hv the choice to not expand this and keep it as is for an answer
2y(27x³+y³)(9x²-4y²)

wintry cape
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I did go further

normal hollow
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I know that u went further and u did right

wintry cape
normal hollow
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U dont hv any reason to be sorry

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Get some rest

wintry cape
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Let’s attempt to do them on my own first

normal hollow
wintry cape
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3 problems left

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Did I do number 21 correct

normal hollow
wintry cape
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Yippee now I can say dos problems left

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I probably did this wrong but I’m unsure

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Where to go with this

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Number 22

normal hollow
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Notice that u can take 2(x+4)⁵ common from each term

wintry cape
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Ok what do you do with the left ^2

normal hollow
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Expand,most likely

wintry cape
normal hollow
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(x+y)² formula

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(x+4)²=x²+2.4.x+16

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this is wrong btw

wintry cape
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How would I go about it then

normal hollow
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$2(x+4)^{7} -36x(x+4)^{5} =2(x+4)^{5}[(x+4)^{2} -18x]$

rocky lotusBOT
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vικτιμιζερ

normal hollow
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$2(x+4)^{5}[(x+4)^{2} -18x]=2(x+4)^{5}[x^{2}+2.4.x+16-18x]$

rocky lotusBOT
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vικτιμιζερ

normal hollow
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Now factorize the 3rd bracket portion

wintry cape
wintry cape
normal hollow
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2×18=36

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I took 2 common as well

wintry cape
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So then wouldn’t the 2 become 1

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I’m confused

normal hollow
wintry cape
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You made the 36 into 18
Wouldn’t the 2 also change to just 1

normal hollow
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Lemme write it down ig

wintry cape
normal hollow
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See if u get it now

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If not mark it

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If yes,then proceed with factorizing x²-10x+16

wintry cape
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Is that a 2

normal hollow
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Yes

wintry cape
# normal hollow

I still don’t really see how you went from this to that
And also what do the 3 lines supposed to show

normal hollow
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Squared

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2 and (x+4)⁵ r the GCFs

wintry cape
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U have a line under that too

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Tbh I’m a lot more confused now 😭

normal hollow
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Okay see 5xy-10x²y
The gcf is 5xy
So u write 5xy(1-2x)

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That's what i m doing

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Do u know this that x⁵.x⁶=x^(5+6)=x^11

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It's the same (x+4)^7=(x+4)^(5+2)=(x+4)^5 .(x+4)^2

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I took the (x+4)^5 common
Which leaves a (x+4)^2

wintry cape
normal hollow
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Yes

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. Or ×

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Both r multiplying

wintry cape
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I see

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U just broken it up

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But going back to the 36 and 2

normal hollow
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See 2y -36x
Gcf is 2
So 2(y-18x)

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Right?

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Similarly 2(x+4)⁷ -36x(x+4)⁵
=2(x+4)⁵[(x+4)²-18x]

normal hollow
wintry cape
wintry cape
# normal hollow

I know your saying you just did 2(y-18x) and it makes sense like that but nothing is written like that in what you broke down here

normal hollow
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I think u should try to solve it urself,and then u will understand

wintry cape
normal hollow
normal hollow
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Take rest,do this later

vale dockBOT
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@wintry cape Has your question been resolved?

wintry cape
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But I really wanna understand what I’m doing

rigid pivot
wintry cape
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Number 22

marble arch
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take 2(x + 4)^5 common

wintry cape
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I’m looking back is this basically what im doing

rocky lotusBOT
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xfilin

wintry cape
rigid pivot
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This is what you need to do

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I’ll give you a better explanation

rigid pivot
# rigid pivot I’ll give you a better explanation

To simplify the expression $$2(x+4)^{7}-36x(x+4)^{5}$$, we first look for common factors.Identify the common factors: Both terms have a factor of 2 and a factor of $$(x+4)^{5}$$Factor out the common terms: We pull out $$2(x+4)^{5}$$ from both parts of the expression.$$2(x+4)^{7}$$ divided by $$2(x+4)^{5}$$ leaves us with $$(x+4)^{2}$$$$-36x(x+4)^{5}$$ divided by $$2(x+4)^{5}$$ leaves us with $$-18x$$So, the expression becomes $$2(x+4)^{5}[(x+4)^{2} - 18x]$$Simplify inside the brackets: We expand $$(x+4)^{2}$$ which is $$x^{2} + 8x + 16$$Now, the expression inside the brackets is $$x^{2} + 8x + 16 - 18x$$Combine like terms: We combine the 'x' terms: $$8x - 18x = -10x$$The expression inside the brackets is now $$x^{2} - 10x + 16$$Factor the quadratic: We need to find two numbers that multiply to 16 and add up to -10. These numbers are -2 and -8.So, $$x^{2} - 10x + 16$$ factors into $$(x-2)(x-8)$$Final Answer: Putting it all together, the simplified expression is $$2(x+4)^{5}(x-2)(x-8)$$

rocky lotusBOT
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xfilin

rigid pivot
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Brodie💀 I think I’m locked in

rigid pivot
rigid pivot
wintry cape
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How do you go from there to there

wintry cape
marble arch
wintry cape
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Does that count

marble arch
wintry cape
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And I’ve went do a lot of other work

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Cus I’ve been on the same math worksheet for hours

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And my teacher is practically impossible to understand and deal with

wintry cape
wintry cape
rigid pivot
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Yes?

marble arch
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I've honestly got no clue dude, who wrote it?

wintry cape
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Also can you guys see this class notes and see if that’s what we are doing here
Maybe I learned it another way and you guys are showing it another and I’m confused that way

OR

it’s just a complete different topic and I’m sleep deprived

wintry cape
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I was tryna process your break down

wintry cape
rocky lotusBOT
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xfilin

rigid pivot
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Do you understand it now or do you not get something?

wintry cape
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I’m still on abt the -18x bc Im not grasphing that- how did you get that

rocky lotusBOT
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xfilin

rigid pivot
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What do you think?

wintry cape
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👍

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We are left w ??

wintry cape
normal hollow
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Wow r we on the same math now

wintry cape
normal hollow
wintry cape
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Still are on the same equation.

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If that’s what u mean

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I think I’ve figured out this is the same thing as u substitution

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You guys were showing it to me a different way then I learned it

normal hollow
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Oh so plug in x+4=y

normal hollow
wintry cape
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Yeah I did all of that

wintry cape
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But that’s why I was so unfamiliar

normal hollow
wintry cape
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Yep working on it

normal hollow
wintry cape
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Can’t thank all of you guys enough omg

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For your helpfulness and support

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I appreciate it plenty

normal hollow
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At the end it was u who solved it thopandawow

wintry cape
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I hope to develop the amount of patience you all have

marble arch
wintry cape
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I did the last one

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Am I done

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Pls tell me i done

marble arch
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Yes, you're done, that's correct!

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NOW GO REST!!!

runic scroll
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just coming in to say, well done!

wintry cape
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All of you are amazing 😭 thank you so much

I am happy to say

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U can close this ticket

marble arch
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You gotta do it mate

wintry cape
marble arch
wintry cape
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Till I see u again 👋 @marble arch @normal hollow

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.close

vale dockBOT
#
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vale dockBOT
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river arrow
#

a most curious math problem appeared on the server some time ago and filled me with zeitgeist. i finally found an equation for the answer but im not sure how to unravel the trigonometry. any hints would be appreciated orz $\frac{\sin(3x)}{\sin(135-3x)} = \frac{\sin(x)}{\sin(45-x)}$

rocky lotusBOT
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Plvzfq_rit

river arrow
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(have to solve for x)

marble arch
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Have you tried opening sin(3x)

river arrow
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like thru a trig identity?

marble arch
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Yes, sin3x = 3sinx - 4sin^(3)x

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unless I'm mistaken

river arrow
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i havent yet no

marble arch
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Whoa, that might just do it I realised

river arrow
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hmm lemme try that, as well as open out the other stuff

marble arch
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Alright sure, let me know once you get it (which you should unless there's a gimmick or I'm missing something)

river arrow
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ok... i think i mightve gone astray and did something wrong with my calculations

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first i tried to expand the stuff at the bottom

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$\frac{\sin(3x)}{\sin(135)\cos(3x)-\cos(135)\sin(3x)} = \frac{\sin(x)}{\sin(45)\cos(x)-\cos(45)\sin(x)}$

rocky lotusBOT
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Plvzfq_rit

river arrow
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then those constants have special values, so i could do...

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$\frac{\sin(3x)}{\cos(3x)+\sin(3x)} = \frac{\sin(x)}{\cos(x)-\sin(x)}$

rocky lotusBOT
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Plvzfq_rit

river arrow
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hmm from there i tried expanding the left hand side with the reduction formula so...

marble arch
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No no

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sin(135 - 3x) = sin(3(45 - x))

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That's also sin3, well, let's say y, that's also sin3y

river arrow
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oh! yes

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dang i didnt realize that, thanks

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lemme try this again

marble arch
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No problem mate

river arrow
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hmm

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should i have gotten $\sin^2(x)=\sin^2(45-x)$ in the end?

rocky lotusBOT
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Plvzfq_rit

river arrow
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hmm i think i got it

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yep this should be good

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thanks again doctorstrangejr!

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.close

vale dockBOT
#
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vale dockBOT
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scenic zealot
#

Can I show a causal link between data using a line graph?

turbid summit
#

you mean linear regression? thonk

scenic zealot
turbid summit
#

you use regression for that...

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but corelation is not causation so i'm not sure

scenic zealot
vale dockBOT
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lime dome
#

it was supposed to be a 3 letter code and i thought the one for bifid was the easiest. However, i think i messed up since i got tabonexo myosorfs for the qclxqjpo poojjsrc

lime dome
#

im stuck on deciphering this

sour needle
lime dome
sour needle
#

110 = 6,
1 2 3 4 5 6
a b c d e f

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#

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lusty bay
#

ignore hte numbers and letters (its from a random youtube video)

the circle on the left is split into many (proper) triangles like shown on the left. then its rearranged to from that rectangle... yeah, if hte radius is 10, how much longer will the rectangle be from the circle?

so he wants to compare between the diameter of the circle and the longer length of the rectangle. the diamter of the circle is 2r., and the longer length of the rectangle is basically the circumference of the circle (this is my thought process, not stating facts)

so that should be 2 pi r - 2r ---> 20 pi - 20 --> which has pi...? the answer doesnt have pi in it

lusty bay
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or thats how it was shown in the video.

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the answer is like... 20?

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where did i go wrong

stark wedge
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the answer doesn't have pi in it

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uhhh what. 20???

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you're gonna have to link the video cause you're not making any sense rn

lusty bay
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I changed the given information so ignore the 20.

stark wedge
#

the rectangle, if we imagine its imperfections to be small enough not to matter, has height r and length pi r

fickle rose
jovial edge
#

Maybe they round up the answer so pi isn't in here?

lusty bay
#

the video is random and embarassing nobody judge me 😡.

stark wedge
#

i mean we're trying to get to the bottom of your confusion not judge you

pine prairie
lusty bay
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the video

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give me one second

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ill link it

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im just finding the proper timestamps

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15:22 for the question
18:01 for the right answer (10)
i changed the context from diameter to radius but that shouldnt add a pi

https://youtu.be/VMHCyzTP4oE?si=szwcVd-3PGYnCl6h

Migaku is offering a 50% discount on their Lifetime subscription, along with an additional free month on Standard and Early Access subscriptions: https://migaku.com/CantoMando

We are switching things up a bit! This week we are putting Sheldon, a Mechanical Engineer, up against a Chinese 5th grader to see who is smarter? Chinese kids have been k...

▶ Play video
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if you comment on the choice of video

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i will find you,

lusty horizon
#

Okay

stark wedge
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hm

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ok so the English of this problem ain't so great

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but what i THINK is happening

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is that they're asking for the difference between the shapes' perimeters.

lusty bay
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would that justify the existance of pi

stark wedge
#

and this difference, to put it simply, consists entirely of the 2 vertical sides of the rectangle.

#

so the answer really is 2r

pine prairie
#

um

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did you watch the explanation

lusty bay
#

i didnt understand.

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nor did i comprehend how he started it.

lusty bay
stark wedge
#

i... dont understand what is unclear

pine prairie
#

you got xy'd in a video

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lmao

lusty bay
#

that still gives pi

pine prairie
#

hypotenuse of the 2 lengths r and 2 pi r?

lusty bay
#

like a right triangle in the rectangle

pine prairie
#

there are no right angled triangles in this problem

lusty bay
#

from a right triangle that splits the rectangle in half

pine prairie
#

afaik there arent even triangles in this problem

lusty bay
pine prairie
#

that's not the problem

#

these 3 sided shapes dont have 3 straight sides

lusty bay
pine prairie
#

look at what the kid draws

lusty bay
pine prairie
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see how his sides are bumpy

lusty bay
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OH

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oh...

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yeah we dont straighten up the circumference of the circle

pine prairie
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he claims that the 2 bumpy sides are just the exterior of the circle

lusty bay
#

nice.

pine prairie
#

so they will be just the same as the circumference in length

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so the difference will just be the extra 2r pieces on the 2 ends

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so the differences is 2r = d = 10

lusty bay
pine prairie
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yeah that's what the kid said

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im just repeating what he said lol

lusty bay
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the kid spoke too quickly.

pine prairie
#

it helps that i understand whats hes saying rather than the shitty subtitles

lusty bay
#

why did they give him this misleading shape

pine prairie
#

ya the question was bad

lusty bay
#

but not it exactly

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wdym the diameter is equal to the circumference in length

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isnt that the whole point of pi that they arent

pine prairie
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i did not say that

lusty bay
#

my bad! please elaborate

pine prairie
#

i said

#

the 2 bumpy sides of the rectangular looking shape is just the exterior of the circle

#

so they have the same length

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hence the difference will be the 2 ends of the rectangle looking shape

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which has length r on each side, so together it's 2r = diametre = 10

lusty bay
#

but for rectangle

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this was all a miscommunication bc english si trash

pine prairie
#

yes

lusty bay
#

yeah now it makes sooo much sense

#

ty

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.close

vale dockBOT
#
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jovial edge
#

You can beat the kid keep going opencry

river shale
short solar
#

i just scrolled up , im sorry for the ping

vale dockBOT
#
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light egret
#

Question:
If I have the set A = {1, 2, 3} and I have the relation R = {(1, 1), (2, 2), (3, 3), (1, 3)} (hope my notation is correct), does that mean the relation is reflexive? Or is it not reflexive because we have that (1, 3) in there?

light egret
#

It was something that confused me during lecture

keen tundra
#

reflexive means it contains (a, a) for every a

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it doesn't make sense to disallow any other pair to be in the relation. As this forces any reflexive relation to be the identity

light egret
#

Okay that was what I thought too, thank you

#

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rocky lotusBOT
#

brandon

drifting hornet
#

it's an if and only if, so it depends on which direction you do first

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if you wanna start with the -> direction, then you assume that phi is an automorphism and prove that G must be abelian and has odd order

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you probably only used the fact that phi is a homomorphism for now, so now its porlly time to use the fact that its also an automorphism

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what does that mean? What can you infer about phi?

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into itself

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but thats obvious in this case

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the important part is bijective

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try using the fact that phi is bijective, to prove that G must have odd order

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might be useful to look at some groups of even order and find out why squaring isnt bijective for them
(ping me if u need me)

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indeed

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or wait

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if such element exist, then it's not bijective

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but i'd go for contradiction here. Assume it's even, prove that such g exists, get a contradiction (phi is not injective) and conclude it's odd

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lagranges theorem is more relevant for the other direction tbh

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at least i think so

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do you know what order of element is? Do you know that it divides the order of the group?

keen tundra
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minimal n

drifting hornet
#

and do you know that order of any element g divides the order of the group G

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or that order of any subgroup of G divides order of G itself

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oh now thats even better

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think about how u could apply it here

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and think about how this relates to order of element (how u could rephrase it in terms of orders)

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soo...?

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yeah, and as you said before, g^2 = e gives you contradiction (bc that means phi(g) = g^2 = e = e^2 = phi(e), which contradicts injectivity)

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and so the first dir is done

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yep

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the fact that its a homomorphism is quite trivial, so the only difficult part is gonna be the bijectivity

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good thing is that for functions G -> G for finite G, injectivity = bijectivity = surjectivity, so for the other part you're just gonna have to prove injectivity

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well, to start, id try reducing it to something^2 = e, youve already dealt with that once and its generally a bit nicer

light saddle
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(i.e. always look at the Ker to prove a homomorphism is injective)

drifting hornet
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do you know what a kernel is?

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kernel is basically the set of all inputs to a function, which result in e when plugged in

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i.e. {x | f(x) = e}

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and to prove that a homomorphism is injective, it suffices to prove that the kernel is trivial (i.e only contains e itself)

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but if this is all new to you, dw about it

drifting hornet
#

and once you're done, dig deep in your memory or notes and try to recall the lagrange's theorem. Im fairly sure you already know it, since you know cauchy's theorem.

Lagrange's theorem says either one of the following:

If H is a subgroup of G, then |H| divides |G|

or

If g is in G, then ord(g) divides |G|

keen tundra
drifting hornet
#

yeah, thats essentially it

#

since G has odd order x=e
This is the step which uses lagrange's theorem btw. G cant have element of order 2, because then 2 would divide |G|, but 2 cant divide odd number

#

>>> something

#

or just > something for one liners

#

np

#

yep

#

you're welcome :)

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marsh lagoon
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distant galleon
#

claim

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distant galleon
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steady charm
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amber gazelle
#

ummm another google sheet formula question welp sorry lol

amber gazelle
#

Option 1 works, but I can't make option 2 to work

#

for example

#

works

#

but if I try sum countif it only reads -1 not 1 cells

hardy coral
steady charm
#

the formula works in excel, but google sheets does not have exactly the same syntax as excel so it doesn't work

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#

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fast bridge
#
sqrt(x)(2x^2+3(x-(2x+1)))

I'm not sure how I can simplify the above problem, mostly because the parentheses seems to soft lock me into the things I'm allowed to do to equation.
I've managed to get it down to

sqrt(x)(2x^2+3x - (6x+1)

by distributing the 3 but I dont know where to go from here

hazy pivot
#

!original please

vale dockBOT
#

Please show the original problem, exactly as it was stated to you, with the entire original context. A picture or screenshot is best. If the original problem is not in English, then post it anyway! The additional context might still be helpful. Do your best to provide a translation.

hazy pivot
#

Just to be sure that you're writing it correctly for us

fast bridge
hazy pivot
#

Cool

#

Let's start from the innermost expression

#

What's $x - (2x+1)$

rocky lotusBOT
#

Xavier 🌺

fast bridge
#

mmm thers nothing i can do with this here right, I mean maybe distribute a negative 1?

hazy pivot
#

Yes

#

So what does it give you

fast bridge
#

x -2x -1

hazy pivot
#

Good

#

Now can you simplify that further

fast bridge
#

-x-1

hazy pivot
#

Good

#

Now what's $3(-x-1)$

rocky lotusBOT
#

Xavier 🌺

fast bridge
#

-3x-3

hazy pivot
#

Good

#

What's your expression now

fast bridge
#

sqrt(x)(2x^2-3x-3)

hazy pivot
#

Good

#

Now there's only possible thing to do

fast bridge
#

I could distribute the sqrt of x inside

#

I don't think that makes sense actually

hazy pivot
hazy pivot
#

What's your end goal here

fast bridge
#

simplify the expression

hazy pivot
#

I hate that sentence cuz it's not explicit

#

I'd call what you have here simplified enough

#

But sure you could distribute the √x

fast bridge
#

Alright, thanks, it really wasn't as confusing as I thought it would be

#

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regal topaz
#

I feel like I did something wrong

vale dockBOT
regal topaz
#

,rotate

rocky lotusBOT
regal topaz
#

heres the question

#

can someone explain what i did wrong or how i can get to the right answer

modest sinew
# regal topaz ,rotate

U pulled out dy/dx from (y^2 + 2xy*dy/dx + 4*dy/dx) even though the y^2 part doesnt have dy/dx

vale dockBOT
#

@regal topaz Has your question been resolved?

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regal topaz
#

.reopen

vale dockBOT
#

regal topaz
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.close

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green steeple
#

Hey guys I need some help understanding this

green steeple
#

Its asking to evaluate each limit with power rule

flint phoenix
green steeple
#

You bring down the exponent to the coefficent and if there is one already you multiply them together and subtract one from the exponent

leaden rivet
#

Are you evaluating the limit or tryna find the derivative?

runic scroll
#

sorry, accidentally hit my keyboard.

green steeple
leaden rivet
#

Just evaluate? Nothing specific?

green steeple
fossil mulch
#

That's question 32 no?

green steeple
#

yes

fossil mulch
green steeple
#

oh snap my bad i got confused

#

sorry for sending the wrong one

green steeple
#

f prime of x is 1/x^3 right?

fossil mulch
#

No

#

$f(x)=x^{\frac{1}{3}}$

rocky lotusBOT
#

denzio321

fossil mulch
#

Power rule:$f(x)=x^n$ $f'(x)=nx^{n-1}$ where n is a constant

rocky lotusBOT
#

denzio321

green steeple
#

so f'(x)= 1/3x^-2/3?

fossil mulch
#

Yes

#

Then just sub x=5 in there and do some simplification

green steeple
#

What went wrong

vale dockBOT
#

@green steeple Has your question been resolved?

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north scarab
#

This is incorrect apparently

vale dockBOT
north scarab
#

answer key:

stark wedge
#

you forgor the chain rule

#

or rather you didn't differentiate x^(1/2) correctly for it

north scarab
#

let me try again

stark wedge
#

derivative of x^(1/2) is not "just 1/2"

north scarab
#

1/2-1

fossil mulch
north scarab
#

thank u I

#

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mint slate
#

apparently the answer is 17, how to get there

hardy coral
mint slate
#

am i tweaking or drawing that equal 18?

#

or am i geeking

#

oh nvm

#

i am

#

tysm sir

#

and or mam

#

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final swift
vale dockBOT
final swift
#

Did I set it up correctly?

pure pulsar
wild linden
#

That looks correct to me

final swift
pure pulsar
#

Where’s the final answer

pure pulsar
final swift
#

oh like 25(cos^2(x)-sin^2(x)) = 25(cos(2x))

#

i get -20pi

pure pulsar
#

Yeah

#

Do that and then solve

pure pulsar
final swift
#

I got -20 pi

#

oh im stupid i wrote pi not pi/4

#

sorry

wild linden
#

Not stupid. Just learning.

pure pulsar
pure pulsar
final swift
#

yeah

pure pulsar
final swift
#

ah

#

i got the right answer yay

#

it took me 4 tries to do this question man

#

thanks

#

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pure pulsar
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fathom narwhal
#

how to solve the konesinberg bridge therrrom

fathom narwhal
#

Theorem

coral urchin
#

eulers criterion

#

that there exists an eulerian path <==> exactly 0 or 2 vertices have an odd degree

thin valley
#

I think he means how to solve the particular case the Königsberg problem. The euler's criterion is the general theorem to prove to solve it so applying it without reasoning is an act of faith in this case. I suppose he is interested in the proof of the criterion

coral urchin
#

i believe it comes from handshaking lemma and def of eulerian path

thin valley
#

So first thing you have to realise is that you can represent the problem with a graph

#

The problem is solved if you can find a path on the graph that passes through every edge just once finishing in a distinct or the same vertex

#

Are you there?

#

So suppose a general graph and a path on that graph for which that holds. The vertices in the middle can only be connected with an even number of edges (even degree) because when you go into one of them you always go out. This means the only vertices that can have an odd number of edges are the first one and the last one (two vertices of the graph)

A graph is eulerian if and only if it has 0 or 2 vertices with odd degree. (If it has two, every possible path goes from one of such vertices to the other).

Every vertex of the Königsberg has an odd degree, so one cannot find an eulerian path on it

vale dockBOT
#

@fathom narwhal Has your question been resolved?

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final swift
vale dockBOT
final swift
#

The answer should be 81pi/5 for the volume

#

did i set it up wrong

cerulean scaffold
#

Could you post the question as is?

final swift
coral urchin
#

81pi/5 is correct

#

although, if you use shell method, you dont have to covert everything wrt y

#

OH youre saying you didnt get 81pi/5

#

sorry

#

so, the shell method says that if we rotate about $x=h$, then $$V=2\pi\int_a^b(h-x)f(x)dx$$ for $a<b\le h$

#

i would use this method instead of washers and chasing y around

rocky lotusBOT
#

Cycadellic

final swift
#

i think we didn't learn this one

coral urchin
#

hmm

#

but this is the entire setup to a shell integral

#

i mean, we can do washers anyways

final swift
#

if i use the shell method is it $$V=2\pi\int_0^1(2-x)(27x^3)dx$$

rocky lotusBOT
coral urchin
coral urchin
# final swift

also, if you want to stick with washers, your setup is wrong

#

we subtract 2, not add it

final swift
#

why subtract

coral urchin
#

so the line we rotate about is moved to 0

#

if that makes sense

#

then its just usual washer from there at 0

#

hence $$V=\pi\int\left(((h-R_0)^2-(h-R_1)^2\right)dx$$

rocky lotusBOT
#

Cycadellic

final swift
#

i see

fathom narwhal
#

.reopen

vale dockBOT
#

@final swift Has your question been resolved?

final swift
#

i tried both methods but i get a wrong answer for the washer method even tho i should get same answers

coral urchin
#

Why is your upper bound 8 now?

#

27 was correct

final swift
#

this is another question, same type but different numbers

coral urchin
#

Oh

#

The setup is correct

#

The problen is the second step

#

You say
3-y^(1/3)+1/4 y^(2/3)
when it should be
3-2y^(1/3)+1/4 y^(2/3)

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turbid pike
#

can someone explain why this is logically true?

stark wedge
#

wym "logically"

#

this has very little logic or reasoning, it's just bashing

turbid pike
stark wedge
#

sure is.

turbid pike
#

i thought it had some reasoning too

stark wedge
#

that's it.

coral urchin
jovial edge
#

maybe you want a combinatorial proof ?

turbid pike
jovial edge
#

I meant do you really want that since combinatorial proof can get a bit tricky compare to the algebra one

turbid pike
#

still thanks tho

rocky kettle
#

lol i just proved this problem 1 week ago in math lesson xD

jovial edge
rocky kettle
#

you should've seen my classmates face

rocky kettle
#

you just need pascal triangle for that

turbid pike
rocky kettle
#

logically is just pascal triangle

limber cliff
#

Why u need any reasoning?

rocky kettle
turbid pike
jovial edge
#

Given a set A={a,b,c,.....}

turbid pike
jovial edge
#

this set has n+1 elements

#

I choose r elements in this set

rocky kettle
jovial edge
#

I have rCn+1

rocky kettle
#

its a triangle of which all the lines depends on the previous one

#

essentially just the 2 numbers above added together

jovial edge
#

On the other hand, I divide this into 2 cases

rocky kettle
turbid pike
#

who shd i listen to?

jovial edge
#

1 that in r elements i choose, there is element a

rocky kettle
#

i think mine is simpler

jovial edge
rocky kettle
#

ok you first then

jovial edge
rocky kettle
#

ping me when you're done

turbid pike
#

tbh not interested in knowing the reasoning now

#

anyways thanks and osrry you two

#

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jovial edge
turbid pike
#

.reopen

vale dockBOT
#

turbid pike
#

.close

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midnight pier
vale dockBOT
midnight pier
#

Where did I messed up

#

Answer was suppose to be 1/2

keen tundra
#

(1-sqrt(u))(1+sqrt(u)) is not 1-u^2 its 1-u

midnight pier
#

Omg no way I just did that mistake

#

Embarrassinggg!!!

midnight pier
#

.close

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cursive ridge
#

Hello, my lecturer give me a method for this exercise but i quite don’t get it. Can anyone help

copper stump
#

You got A as
$ \begin{pmatrix}
2020 & 1 & -2020 \
2019 & 2 & -2020 \
2019 & 1 & -2019
\end{pmatrix} $

rocky lotusBOT
#

Βαχτερ10Φρ4γ

copper stump
#

and you need to find B according to the hint, can you do that?

cursive ridge
#

B= A - I

#

Is it?

copper stump
#

indeed

cursive ridge
#

So what will I do next

copper stump
#

your teacher also told you B^2 or B^3 = 0

#

you can try to find what exactly is the B matrix, and what powers of B are all 0

#

and replace the values in the expression you have to find

cursive ridge
#

Hm how can i find it

copper stump
cursive ridge
#

What about B^2 and B^3

copper stump
#

did you find the B matrix?

#

nature of B directly tells about that

cursive ridge
#

Here it is

#

I just dont understand the connection between these

copper stump
#

now can you do B^2?

#

notice how all the rows are identical?

#

that would be helpful for the matrix multiplication

vale dockBOT
#

@cursive ridge Has your question been resolved?

cursive ridge
copper stump
#

no

#

I meant it make matrix product simpler

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#
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copper stump
#

you can also notice that the sum of all the row elements (2019 + 1 + (-2020)) is 0

#

.reopen

vale dockBOT
#

cursive ridge
#

Thank u

#

I got it

#

.close

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midnight pier
#

the formula to find the area of a circle is πr², but what do I get if I just use r²? i asked AI but it confused me more

hardy coral
#

... you get 1/π of the area of the circle

wintry oxide
#

What are you trying to achieve ?

midnight pier
outer belfry
hardy coral
#

You also get the area of that smaller section of the circle, where the arc BC has length 2AB (in other words, angle BAC is 2 radians)

#

That area and the area of the square from @outer belfry are equal

midnight pier
#

π is the ratio of a circle's circumference to its diameter, how multiplying the square area to π gives the area of circle?

#

sorry for these stupid questions but i really want to understand it

hardy coral
#

You can find lots of proofs of that online; not sure anyone can explain it clearly without using a proof

midnight pier
#

ok thanks

hardy coral
#

Here's a simple argument for example:

#

The area of the regular polygon is OA times its perimeter, because each of these triangles have area OA times the side length divided by 2, and there are as many triangles in the polygon as the polygon has sides

#

As you increase the number of sides, OA approaches the radius of the circumscribed circle, and the perimeter approaches the circumference

#

So the area is simply the radius times the circumference divided by 2

#

-> r * 2πr / 2 = πr²

outer belfry
#

In our local primary school textbooks, they usually have similar "diagram" like these to "explain", non-rigorous of course:

midnight pier
#

i got it

#

thank u

#

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neat tusk
#

show steps of solving this binomial theorem problem

pure mirage
neat tusk
pure mirage
# neat tusk no

Do you know the general formula for the binomial expansion?

pure mirage
#

\li \ [(a+b)^{n}=\sum_{k=0}^{n}\binom{n}{k}a^{k}b^{n-k}] i.e. for the first you have [(ax^3+b)^{8}=\sum_{k=0}^{8}\binom{8}{k}a^kx^{3k}b^{8-k}]

rocky lotusBOT
pure mirage
neat tusk
pure mirage
#

Just that those equations hold

neat tusk
#

i do

pure mirage
# neat tusk i do

Alright. Well, now on the right side there is the binomial expansion of the left and we want to see what coefficient $x^6$ has. The right side looks like [(\text{some coefficient}_1) x^0 + (\text{some coefficient}_2) x^3 + (\text{some coefficient}_3) x^6 + \dots][ + (\text{some coefficient}_8) x^{24} ]

rocky lotusBOT
pure mirage
#

I.e. we just want to look at that one summand with x^6, right?

#

And ignore all the rest

pure mirage
neat tusk
#

got it

pure mirage
#

The second sum here represents this addition of all the coefficient * x terms

#

We just need to find what k we should be looking at

#

Well, when is x^(3k) = x^6, for what k?

pure mirage
#

This thing

#

is just this in a more compact form:

neat tusk
pure mirage
pure mirage
clever sentinel
#

@neat tusk Do you know the binomial expansion?

neat tusk
clever sentinel
#

Can you write it here or send an image? It will be good if you write the binomial expansion of (ax³+b)⁸

clever sentinel
#

you just need to write the first 2 terms and then the last term and use "..." between them

clever sentinel
neat tusk
pure mirage
#

[this is what the notation with the Sigma (looking like an E) does in a short form; the k's are running from 0 to n, but if you hadn't had it then yes, write it as you know it]

clever sentinel
marsh whale
clever sentinel
#

@neat tusk We can continue after you send the general binomial expansion formula which looks something like (a+b)ⁿ or (x+a)ⁿ. It should be present in your notes or in your book.

vale dockBOT
#

@neat tusk Has your question been resolved?

vale dockBOT
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wet sundial
#

need help checking Q from H/W

vale dockBOT
hardy coral
#

Looks correct catthumbsup

stark wedge
#

wait a minute

#

your work for Q1 looks cut-off or undone

coral ocean
stark wedge
#

G1 does not have an Euler circuit, because the degree of vertex E is odd integer and-
what next

stark wedge
#

2 allows an euler path but no circuit

coral ocean
coral ocean
wet sundial
#

wait whats the diff betwwen path and circuit again?

stark wedge
#

whether you finish back where you started

coral ocean
#

and Euler circuit you meet every point only once?

hardy coral
coral ocean
#

okay ty

hardy coral
#

A path doesn't necessarily have the same end points

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(a circuit is a path)

stark wedge
#

thing is that if your graph has 2 odd-degree vertices then an euler path must start at one and end at the other

wet sundial
#

so its correct?

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(other than hanging sentence)

hardy coral
#

"G does not have an Euler circuit because the degree of at least one of its vertices is odd"

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If that's what you meant, then yes

wet sundial
#

ok thanks

#

.close

vale dockBOT
#
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opal pendant
vale dockBOT
opal pendant
#

i found alpha = sqrt(2) by putting it in the curve

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now im thinking i differentiate the curve twice? but im getting such an annoying expression

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and im not able to do anything

safe fulcrum
opal pendant
#

😭

safe fulcrum
#

,w (2x + 2y * u) + 5(x^2 - y^2 - 1)^4 * (2x - 2y * u) = 0, solve for u

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u = y' btw

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sigh, I'll just use Symbolab to confirm your 1st derivative

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yeah okay if the 1st derivative is still that impossible, hmmm

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I think it's a product rule in disguise, yeah

safe fulcrum
#

if it were -3y^2 y' - y^3 y'', it would be easier

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but unfortunately it's not

opal pendant
midnight iris
opal pendant
safe fulcrum
midnight iris
safe fulcrum
#

you have to algebraically find the 2nd derivative and then sub in

midnight iris
opal pendant
safe fulcrum
#

apparently it's like this

opal pendant
safe fulcrum
opal pendant
#

this dosent look humanly possible to calculate 😭

#

esp under time constraints

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but i guess my q is clarified

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thank u

opal pendant
#

its asking 3y'

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y' = dy/dx

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why would u differentiate wrt y

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and even if we do

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why would we treat x as a constant

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.close

vale dockBOT
#
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cosmic lichen
#

a,b,c are natural numbers

vale dockBOT
cosmic lichen
#

Suppose that
a²+3b²=2c²

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Prove that b is divisible by 9

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First I tried doing mod 3

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So that
a²≡2c²

Every square number have either 0,1 mod 3
If a²≡1
1≡2
Is wrong
So a,c ≡0 [3]

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So I wrote that
a=3k
c=3m

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9k²+3b²=18m²

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Devide by 3
3k²+b²=9m²

opaque stratus
#

are you guys math majors discussing these

cosmic lichen
#

Take mod 3 again i suppose

fickle rose
cosmic lichen
#

So b²≡0
So b≡0 [3]

fickle rose
#

oh wait I see, okay nodnodnod

cosmic lichen
fickle rose
cosmic lichen
#

Then again I suppose b=3n
So b²=9n²

cosmic lichen
cosmic lichen
#

3k²+9n²=6m²

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Then wat

keen tundra
#

divide by 3, you have the original equation back

fickle rose
#

note that that's your equation again, just divide by 3

cosmic lichen
#

Yeah

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So k²+3n²=3m²?

midnight iris
#

try contradiction?

cosmic lichen
#

But maybe

hidden terrace
rocky lotusBOT
#

Miyagi

cosmic lichen
midnight iris
#

well then b/9 will be some p/q

cosmic lichen
#

K²+3n²=2m²

midnight iris
#

and then we can just prove that p/q is irrational

#

right?

fickle rose
#

well you've shown that we can write (a^2+3b^2=2c^2) as (k^2+3n^2=2m^2) after taking out a three factor from all terms

rocky lotusBOT
#

PajamaMamaLlama

fickle rose
#

just repeat again

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and you have divisiblity by 9

cosmic lichen
cosmic lichen
fickle rose
#

I will do a rewrite to make it clearer

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(k:=a_1, n:=b_1, m:=c_1)

rocky lotusBOT
#

PajamaMamaLlama

cosmic lichen
#

Ok

fickle rose
#

we get from (a^2+3b^2=2c^2) to (a_1^2+3b_1^2=2c_1^2)

rocky lotusBOT
#

PajamaMamaLlama

fickle rose
#

with (b=3b_1)

rocky lotusBOT
#

PajamaMamaLlama

fickle rose
#

repeat the same argument as before to get (a_2^2+3b_2^2=2c_2^2)

cosmic lichen
#

Ohhh

fickle rose
#

then it must follow (b=3b_1=3(3b_2))

rocky lotusBOT
#

PajamaMamaLlama

cosmic lichen
#

So just take mod 3 again?

rocky lotusBOT
#

PajamaMamaLlama

cosmic lichen
#

Tysm

#

Another n question may I ask?

#

oke 1 min

hidden terrace
#

What happens if you repeat the process indefinitely?

cosmic lichen
#

x,y are non-negative integers.
Prove that we can write any non-negative integer as 5x+3y, except for these numbers (1, 2, 4, 7).

cosmic lichen
hidden terrace
cosmic lichen
#

How

hidden terrace
#

The GCD of any two numbers x, y can be written as ax + by

fickle rose
cosmic lichen
hidden terrace
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Yes

cosmic lichen
#

What is it

hidden terrace
#

I'll link a video if you're interested

cosmic lichen
#

Okay

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But then what

cosmic lichen
#

Then wat

hidden terrace
#

I'll take a different approach actually

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So it's obvious that 1, 2, 4, 7 are the only numbers under 10 that can't be written as 5x + 3y

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We have 8 = 5x1 + 3x1

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9 = 5x0 + 3x3

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10 = 5x2 + 3x0

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Also, if n can be written in that form, then n+3 can too

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So by induction, all numbers greater than 8 satisfy the result

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Does that make sense

vale dockBOT
#

@cosmic lichen Has your question been resolved?

cosmic lichen
hidden terrace
#

We know that 8, 9, 10 can be written as 5x+3y

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And that n+3 = 5x + 3(y+1)

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Which means that 8+3=11 satisfies the condition

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So does 14, 17, and so on

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Repeating for 9 and 10 gives the rest of the numbers above 8

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Since 3 also satisfies the condition, only 1, 2, 4, 7 do not