#help-17

1 messages · Page 42 of 1

trim walrus
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Oh ye

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Inequality change

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When dividing by neg

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I'm dumb

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Thanks

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trim walrus
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Hi again

vocal sleetBOT
trim walrus
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Well

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I tried putting m=2 n =3
and I considered 2 cases 0 and 1
And got f(5) > 2

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As I thought 2005 = 2000 + 5

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I must be helpful

urban edge
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f(even number)=0

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Thats all i got

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Wait no, hold on

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f(9996+3)-f(9996)-f(3)=0

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You shoild be able to find f(3)

trim walrus
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I'm not sure how should I find f(9996)

urban edge
trim walrus
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Ofc yes

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I'd very happy

urban edge
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ok lol

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first thing, rearrange to get
f(m+n)=f(m)+f(n)

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n always equals 2

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then you can do m=2 then 4 then 6

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And so on

trim walrus
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Alr so f(6+2)= f(6)

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How exactly do we know that f(6) is even

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??

mild flower
trim walrus
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This is the second case

urban edge
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OH

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Crap

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Apologies

mild flower
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what could f(3) be though?

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or maybe it's best to see what f(1) could be first

trim walrus
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And how exactly, are we gona find f(1)

mild flower
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we have a constraint

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we might not be able to get it down to one value

trim walrus
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m=3, n=-2

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Smth like this?

mild flower
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what are the properties of f that we know?

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i count six listed in the description

trim walrus
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n can't take neg

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f(3-2) - f(3) -f(-2)

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This would be invalid

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Then

mild flower
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correct, f isn't defined at -2

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so property number 1 is that f has a domain of the natural numbers

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what's the next property we have?

trim walrus
mild flower
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we know its domain, it seems natural to figure out its range

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or at least codomain / try to get a handle on its range even if we don't know the full extent of it

trim walrus
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The only question is how now...

mild flower
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well

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the second phrase of the question would tell you

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although it's phrased kind of oddly

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i read that as saying the function takes on values that are non-negative integers

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where "takes on" I read as "can output"

trim walrus
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Alr

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So our range starts from 0

mild flower
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and is integers

trim walrus
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Yep

mild flower
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so now again what can f(1) be? we know it can be one of 0, 1, 2, 3, 4, 5, 6, ...

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we do have four more properties of f that are given in the question

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three of which are simple and one of which is fairly complicated to state

trim walrus
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Three of which are f(2)=0, f(3) > 0 and f(9999)=3333

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And the fourth one...

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?

mild flower
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the long one

trim walrus
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And even the long one as two cases

mild flower
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well, as two possibilitids

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you could phrase that as f(m + n) - f(m) - f(n) < 2

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but that's maybe less helpful

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but you have everything you need to calculate f(1) or at least to constrain it to a handful of values

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for example, is it possible that f(1) = 20?

trim walrus
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Ig not

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Or maybe it might be

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Well m and n can take any integers but if we take a negative it won't be valid...
And only way to write one is 0+1 (in form of integrs >= 0)

mild flower
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true, so f(1) can't be broken down into m and n

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but that relationship applies to all values

trim walrus
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Yes...

mild flower
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the only useful piece of information we really have right now is f(2)

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because even though f(9999) - f(9998) - f(1) = 0 or 1 we don't know f(9998)

trim walrus
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Yep..

mild flower
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think backwards

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spoiler: ||m = n = 1 - set up the equation and you'll get one possible value for f(1)||

trim walrus
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Considering 0;

f(1+1)-f(1)-f(1) =0
-2f(1)=0
f(1)=0

Considering 1;
f(1+1)-f(1)-f(1)=1
F(1)=-1/2 [invalid]

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We got f(1)=0

mild flower
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yep

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cool! so now you should be able to fill in the rest of the table all the way up to 9999

trim walrus
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Not sure what you mean by that...

mild flower
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what's f(3)?

trim walrus
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Well,
f(3) = 1

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As 2+1

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f(2+1)

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We might find f(5) now

mild flower
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how did you get that f(3) was 1? you're right but I'm not sure your reasoning is right

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f(3) = f(2) + f(1) + (1 or 0)

trim walrus
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Cuz

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We reject 0

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Says f(3) > 0

mild flower
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ah ok yep

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just making sure you had the right procedure

trim walrus
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Alr

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If I try finding f(5)
We again end up with 2 cases...
f(5) = 1 and f(5)=2

As f(3+2)-f(3)-f(2)=(0 or 1)
f(5) - 1 = (0 or 1)

mild flower
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okay cool
why'd you skip over f(4)?

trim walrus
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Oh ye

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F

mild flower
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i mentioned a table before; I'd definitely recommend one here

trim walrus
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Table??

mild flower
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of inputs to outputs

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just to keep track of it

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like

x | f(x)
--------
1 | 0
2 | 0
3 | 1
4 | ???
5 | 1-2
trim walrus
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And also f(4) also has two possibilities l

f(2+2)- f(2)-f(2)= (0 or 1)
f(4)=(0,1)

And
f(3+1)-f(3)-f(1) = (0,1)
f(4)=(0,2)

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Like 3 possibilities

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0,1,2

mild flower
trim walrus
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f(3+2)-f(3)-f(2)=(0 or 1)
f(5) - 1 = (0 or 1)
f(5) = (1,2)


f(4+1) -f(4)-f(1)= (0,1)

Considering 3 case of f(4)

f(5) = (0,1), (1,2), (2,3)
trim walrus
mild flower
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oh right it's symmetric duh

trim walrus
twin meteorBOT
trim walrus
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I think we can see a pattern

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After x=4

mild flower
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how can f(5) = 3?

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that doesn't work as f(2+3)

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what i suspect will happen

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is that you'll need to minimize these values to just barely satisfy that last constraint

trim walrus
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f(4+1)

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??

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f(5)-f(4)=(0,1)

mild flower
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it's gotta work for all of them

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no matter what n and m are (as long as they're natural numbers), that equation has to be satisfied

trim walrus
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Ye

hard atlas
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you can determine f(4) exactly

trim walrus
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Yes?

hard atlas
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f(4)=f(2)+f(2)+(0,1) <= 1. and f(4)=f(3)+f(1)+(0,1) >= 1. so f(4)=1

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next it might be better to skip f(5) and first determine f(6)

trim walrus
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Like
f(4)=(0,1)

f(4)=(1,2)

Taking intersection

f(4)=1
Smth like this

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Perhaps

hard atlas
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yes that is what I just wrote down

trim walrus
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Alr

hard atlas
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yes

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now f(5)

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and then continue until the pattern emerges

trim walrus
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The possibility of f(5) = (1,2)

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I don't think we can find exact value of f(5)

As f(3+2) = 1 + (0,1)
f(4+1) = 1 + (0,1)

hard atlas
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actually, f(7) first is better

trim walrus
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Alr

hard atlas
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urgh I'm making mistakes in my head. but anyway, you got the idea now. now its a bit of playing around with the conditions, playing them against each other

trim walrus
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I think we see the pattern after 4

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1 at 4
Then 1,2 at 5
Then 2 at 6
Then again 2, 3 at 7

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Let me calc

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8

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Intersection is (2,3)

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Again

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My brain is hurting broke

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Will solve this later

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Thanks for the help tho

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old niche
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im confused about a midpoint calculator

vocal sleetBOT
old niche
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calculation

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am i tripping or is the midpoint calculated incorrectly

vocal sleetBOT
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@old niche Has your question been resolved?

flat whale
hardy rivet
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Simpson's rule.

vocal sleetBOT
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@old niche Has your question been resolved?

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vast shale
vocal sleetBOT
vast shale
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What am I doing wrong for e) ii

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?

vocal sleetBOT
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@vast shale Has your question been resolved?

vast shale
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<@&286206848099549185>

peak lark
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in the line where you rationalise the denominator, you are multiplying the numerator and denominator by (4-2sqrt(3)) right?

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have another look at how you are multiplying out the denominator

vast shale
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Ohhhh

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I forgot the minus

peak lark
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it actually took me a scary amount of time to spot that mistake lol

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very easy to make

vast shale
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Thank you

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vast shale
vocal sleetBOT
vast shale
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How do I do this?

vocal sleetBOT
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@vast shale Has your question been resolved?

vast shale
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<@&286206848099549185>

dusk mantle
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just jkin

solid sage
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is this hsc seems familiar

vast shale
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😭

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<@&286206848099549185>

rigid kernel
civic drift
vast shale
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I thought this server was made to help people

rigid kernel
vast shale
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Thanks for the help

#

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fickle rose
vocal sleetBOT
fickle rose
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can someone explain this solution to me

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i do not understand

patent nymph
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What is the problem that this is a solution to?

fickle rose
patent nymph
fickle rose
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why did the proof start with 4 x 5? shouldnt it start for 3x4 for the minimum?

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and then the next inequality im confused about

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i feel like im being dumb

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maybe i should leave this

vocal sleetBOT
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@fickle rose Has your question been resolved?

vocal sleetBOT
#

@fickle rose Has your question been resolved?

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viral copper
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$\lim_{n \to \infty} \sum_{k = 1}^n \left ( \frac{k}{n} \right )^n$

twin meteorBOT
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neonperseus

viral copper
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I don't know where I'd begin on this

blissful saffron
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uh oh

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look who got caught

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start by looking at partial sums

viral copper
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shut up derp

viral copper
blissful saffron
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basically

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Define

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$s_n = \sum_{k=1}^{n} \paren{\f{k}/{n}.}^n$

twin meteorBOT
viral copper
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Uh okay

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And then what

blissful saffron
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Wait does

hard atlas
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yes

viral copper
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Does what

hard atlas
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your fears are real

viral copper
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What fears

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Derp what is happening

blissful saffron
hard atlas
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I'm just guessing but maybe he just noticed the terms depend on n

viral copper
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ah

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So uh

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What does that

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Imply for your partial sum

blissful saffron
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Okay I may have defined it wrongly then

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But it still exists

viral copper
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How do these sums help me solving the problem though

blissful saffron
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just fix the partial sum definition

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well

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infinite series is just a sequence of partial sums

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and you can batter it with a bunch of theorems

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like monotone convergence theorem

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and co

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See if the thing converges

viral copper
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It has a finite answer

blissful saffron
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oh it converges

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i guess partial sums are still useful tho

viral copper
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It's e/(e - 1)

blissful saffron
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oh e

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hmm

viral copper
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Which suspiciously looks like a geometric series

blissful saffron
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yeah it reminds me of the

hard atlas
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I'm wondering if maybe you can see this as a riemann sum

viral copper
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But I didn't want to introduce bias by bringing in the answer

viral copper
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It worked

maiden iron
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but we can still try

hard atlas
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yeah the exponent is also bothering me

peak matrix
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$\frac{\sum_{k=1}^{n}k^{n}}{n^{n}}$

twin meteorBOT
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methisalwaysright

peak matrix
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maybe this?

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and limit to infinity

viral copper
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Hmm

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well

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does that help

hard atlas
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well you just run into a infty/infty situation

peak matrix
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geometric series has closed form partial sum, so it might help

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oh wait it's not geometric

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damn

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nvm ignore me

blissful saffron
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how is this manipulation justified

viral copper
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He just factored out n^n

maiden iron
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1/n^n

viral copper
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yeah

blissful saffron
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oh ok nvm I thought you moved it out of the limit

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lol

viral copper
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haram

blissful saffron
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what was the definition for e again

viral copper
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$\lim_{n \to \infty} \left ( 1 + \frac 1n \right )^n$

hard atlas
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putting the fraction on the left is cursed

blissful saffron
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i agree

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also

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x instead of n

twin meteorBOT
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neonperseus

blissful saffron
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thanks neon

viral copper
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If we were to factor out n from here

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$\lim_{n \to \infty} \frac{1}{n^n} \left ( n + 1 \right )^n$

twin meteorBOT
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neonperseus

blissful saffron
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lim (n+1)^n/n^n

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yep

viral copper
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ooo

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Tantalizing

blissful saffron
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looking close actually

blissful saffron
viral copper
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Is it legal to use the binomial expansion on (1 + n)^n here

blissful saffron
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yes

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(why?)

viral copper
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Even if the variable is in the exponent

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Idk maybe it gives us something useful

blissful saffron
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The answer is just due to how limits work lol

viral copper
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Because if we had

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nvm

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Idt it would help

blissful saffron
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Idk if that goes very far tho

viral copper
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yeah

blissful saffron
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Also gosh darn you is this your way of baiting me to do a limit

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Open a help channel with it

viral copper
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And now you're stuck with me

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Helpers Honor

blissful saffron
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truly I am

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unless I decide to go to sleep

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,ti

twin meteorBOT
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The current time for derp_z is 01:42 AM (AWST) on Sun, 02/07/2023.

blissful saffron
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let's ask wolfie

viral copper
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We know the answer

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e/(e - 1)

blissful saffron
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hmm

wind kestrel
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it would be pretty difficult to find the limit using binomial expansion

hard atlas
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WA doesnt know

viral copper
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Man that's literally

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The geometric

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Series

blissful saffron
viral copper
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For e, e^2, e^3...

blissful saffron
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MathIsAlwaysRight may have a point lol

viral copper
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Can each of these limits individually be written as some sort of power of e

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Which then gets GP'd

wind kestrel
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can you write out what you're trying to say lmao

blissful saffron
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he already did

viral copper
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Indeed

blissful saffron
viral copper
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What's the formula for e^x again

blissful saffron
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er

viral copper
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$\lim_{t \to \infty} \left ( 1 + \frac xt \right )^t$

twin meteorBOT
#

neonperseus

viral copper
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Hmm

blissful saffron
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yeah

viral copper
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I think

blissful saffron
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its tight

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right

viral copper
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$\lim_{t \to \infty} \sum_{k = 1}^{\infty} \left ( 1 + \frac kt \right )^t$

twin meteorBOT
#

neonperseus

viral copper
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THIS IS TANTALIZINGLY CLOSE

hard atlas
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so, we have our sum (1/n)^n + (2/n)^n + ... + ((n-1)/n)^n + (n/n)^n. focusing on the second to last term, that's just (1-1/n)^n and converges to e^-1. the others from the right converge to e^-2, e^-3 and so on

blissful saffron
viral copper
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oh bruh

hard atlas
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e/(e-1) is actually the GP for 1/e

viral copper
viral copper
blissful saffron
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Ah yes 1/e^n

viral copper
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I think what denascite said is right

hard atlas
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yeah but its missing details

blissful saffron
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the one which I said is not convergent KEK

hard atlas
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like lag said, you cant just do that

viral copper
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Such as?

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Hmm

hard atlas
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with each new n there are new terms appearing. why is that fine

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and if we kind of write this down where each row represents a certain value of n. we are then doing the limits by column. why is that allowed

viral copper
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I don't get what you're saying

hard atlas
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yeah not sure how to express what I mean without getting out paint

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or typing a bunch

viral copper
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it's alright

blissful saffron
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does neon need to know analysis to justify these lol

flat whale
#

Neon do you know dominated convergence theorem

viral copper
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nope

blissful saffron
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That sounds like analysis lol

viral copper
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sounds sexy

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doesn't anymore

wind kestrel
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it depends on n

viral copper
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n is very very big

hard atlas
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we are roughly switching the order of the limits. we are first letting k->inf and then n->inf

flat whale
blissful saffron
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lesbesgue dominated convergence theorem?

flat whale
#

Right

flat whale
viral copper
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no idea

blissful saffron
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booo

hard atlas
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$\int_{n=0}^{\infty} \int_{k=0}^n \left( \frac k n\right) ^n \dd k \dd n$ in counting measure or something

blissful saffron
#

chapter 2.3, understanding analysis

viral copper
#

omg integrals

blissful saffron
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measure theory starebleak

viral copper
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Wait that's not a nice integral

flat whale
#

I guess squeeze theorem is the last result

viral copper
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yay I know what that is

last creek
#

double integrals bleakcat

hard atlas
#

nah wait I messed up

blissful saffron
flat whale
#

Bound (1-k/n)^n from above by e^(-k)

hard atlas
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that shows that it converges. but does it show that it converges to the correct thing?

flat whale
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And below by something that approaches to e^(-k) you get from binomial expansion

blissful saffron
#

huh neat

flat whale
#

Involves characteristic functions and integrals

viral copper
#

I'll probably just let this go for now

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Especially if it calls for math beyond my level

hard atlas
#

do you have a specific proof in mind? involving char functions?

viral copper
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I hope that was directed to riemann

hard atlas
#

yes

hard atlas
#

can you share?

flat whale
blissful saffron
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love how it ends with

flat whale
#

Characteristic being indicator, not the Fourier transform one

blissful saffron
#

"Can someone please help me?"

viral copper
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Will you close the channels yourselves after you're done?

hard atlas
#

thanks

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ah yes I first thought you meant the fourier ones

flat whale
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Lol yea I realized that after I sent the link

hard atlas
#

but of course using the indicator ones like that is much smarter

flat whale
hard atlas
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I thought somewhere along those lines but not enough to make it precise

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been some time since I've done analysis like that

flat whale
#

Same. No way I can think of this in just a few minutes

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I just Google fast and pretend like I understand

hard atlas
#

I also googled but didnt find it

blissful saffron
#

wow that is clever

flat whale
#

It's a good problem. Love that there are so many solutions

hard atlas
#

yeah its a nice one. and I think I would have gotten it with enough time, so I'm happy with that

cobalt crypt
#

weird that they didnt just apply MCT to the counting measure

cobalt crypt
flat whale
#

Snow you might as well !nosols me

cobalt crypt
hard atlas
#

I mean whether you apply MCT or DCT to counting measure doesnt make a huge difference at that point

cobalt crypt
#

doing it with char funcs is funky notation

hard atlas
#

it removes the dependence on n for the upper bound which was one thing I was struggling with

cobalt crypt
vocal sleetBOT
#

@viral copper Has your question been resolved?

viral copper
#

I don't know has it

hard atlas
#

well we are happy with the solution

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are you?

viral copper
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My satisfaction doesn't matter lol

#

I think it's beyond my level rn

hard atlas
#

well its your channel

viral copper
#

If you're satisfied I'm satisfied

vocal sleetBOT
#
Channel closed

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viral copper
#

Thanks for your time though

vocal sleetBOT
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empty linden
#

something isnt right. i thought only the value inside the bracket must be squared

empty linden
#

so shouldnt it be 2 sqroot(x), and not 4 sqroot(x)?

hard atlas
#

2 is also in the bracket?

#

$(2\sqrt x)^2 = (2 \sqrt x)(2 \sqrt x) = 2\cdot 2\cdot \sqrt x \cdot \sqrt x = 4 x$

empty linden
twin meteorBOT
#

denascite

empty linden
#

but he put the bracket there after

#

oh, nvm

hard atlas
#

he is squaring both sides

#

everything on both sides

empty linden
#

if its an equation, we square the constant behind the sq root?

#

but in an expression, the constant remains unchanged right?

#

if there was no bracket, would we square the 2, or the x only?

hard atlas
#

$2 \sqrt x ^2 = 2 x$

twin meteorBOT
#

denascite

hard atlas
#

if thats what you mean

empty linden
#

yeah but

#

i was just wondering if we should square the constant behind the square root only if its an equation

#

since an equation squares both sides, but an expression doesnt

hard atlas
#

this has nothing to do with whether its an equation or not

#

2 is either included in the bracket or not

empty linden
#

lets say we have csqroot axb. we wouldnt square the c

empty linden
#

so if the question has a bracket, we square it, but if it doesnt have a bracket, we dont?

#

since a bracket applies to the whole thing

hard atlas
#

$2 \sqrt x ^2 = 2(\sqrt x)^2$

twin meteorBOT
#

denascite

hard atlas
#

and 2 is not in the bracket

empty linden
#

yeah, so 2 sqroot(x)^2 is just 2sqrootx

#

since the square cancelled the square root

hard atlas
#

its 2x

empty linden
#

but in this example, he squared the constant behind it

#

which is why im confused

#

shouldnt this be 2x and not 4x?

hard atlas
#

he squared the whole thing

#

you cant just square part of the thing

empty linden
#

thats what i found in one of the answers

hard atlas
#

you dont square anything in there because you havent written down any square

empty linden
#

so it ended up being c sqroota sqrootb

#

so why do we sometimes square the constant, but sometimes not?

#

why do some examples say we squaare the constant behind the root, and sometimes not?

hard atlas
#

this is not about 2 being a constant or not

#

2sqrtx is one thing

#

you are squaring the entire thing

#

because you square both sides of the equality

empty linden
#

what if its not an equation, but an expression?

hard atlas
#

an expression includes the square already. so either the 2 is included in the bracket or its not

empty linden
#

what if its not

hard atlas
#

then you dont square it

empty linden
#

but in this example, we didnt square the c

#

well, the brackets in lns arent necessary but

hard atlas
#

well why should we square anything there

#

there is no ^2 in sight

empty linden
#

to get rid of the sqroot

#

which is how the answer turned out to be ln c + ln a/2 + lnb/2

hard atlas
#

and?

empty linden
#

ok so basically what i got from this is

hard atlas
#

you didnt square anything

empty linden
#

if bracket, then square the whole thing

#

if no bracket, then square whats inside the root

#

thats it right?

hard atlas
#

square the things inside the bracket

vocal sleetBOT
#

@empty linden Has your question been resolved?

vocal sleetBOT
#
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zenith zephyr
vocal sleetBOT
zenith zephyr
#

how do this?

#

why it wrong

paper depot
#

cos^2(8x)...

#

tho it's also sus how exactly you got that expression

zenith zephyr
#

are you postivie on that

#

dont sell bro

paper depot
#

... i'm a woman, don't call me bro

zenith zephyr
#

bro is gender neutral term

paper depot
#

your experience is not universal.

#

you haven't done what is asked for, was my point.

zenith zephyr
#

wdym?

paper depot
#

rewrite the expression in terms of first powers of the cosines of multiple angles

#

you've got a second power in there still

zenith zephyr
#

does this seem right

paper depot
#

dunno let's check

vast shale
#

Siiii

paper depot
#

,w simplify 4sin^2(4x) - (3-4cos(4x)-cos(8x))

paper depot
#

nope

zenith zephyr
paper depot
#

i had WA simplify 2 * (original expression) - 2 * (your answer)

#

if your answer was correct it would have come out as 0

zenith zephyr
#

,w simplify 1/2[3-4cos(4x)-cos(8x)

twin meteorBOT
zenith zephyr
#

bro you sold so hard

#

you sold smh

#

smh smh smh

#

you dont deserve to have the helpful role

#

youre a bot

#

gg

paper depot
#

you chose to double down on it

vast shale
#

What does selling mean

paper depot
#

and now accusing me of being a "bot"

pallid zenith
#

what is selling

hasty pulsar
#

||It's used in the context of a multiplayer online team-based battle game where you give the enemies kills (by dying from them), and your allies will say that you're selling, because you're giving them (free) kills or points.||

flat whale
#

Ann your sales numbers are through the roof

hasty pulsar
#

It seems POV has raged and left the server, channel may get closed.

vocal sleetBOT
#

@zenith zephyr Has your question been resolved?

hasty pulsar
#

What they meant with selling

paper depot
#

how's that apply here

#

what did i sell

flat whale
#

Just gamer rage talk

#

Nothing logical about it

#

.close

vocal sleetBOT
#
Channel closed

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rotund hornet
vocal sleetBOT
pallid zenith
#

whatd you try

boreal star
#

What's the domain of arccos?

rotund hornet
#

-1,1

boreal star
#

So for what domain of x can sin take values in [-1,1]?

boreal star
#

What are the possible values of x such that sin x lies in [-1,1]?

rotund hornet
boreal star
#

Why? What are the possible values x can take, not sin x

#

It should be R, right?

rotund hornet
#

@boreal star

boreal star
#

(-infty, infty)

rotund hornet
#

Ohhhh

#

I though you meant what values can x in sinx take between -1 and 1

#

My bad

boreal star
#

Yeah so the required domain is R then, right?

rotund hornet
#

Yeah

boreal star
#

Now for the range, sin x takes all the values in R, so the range of 2arccos(sin x) should be twice of arccos, right?

rotund hornet
#

Because of the 2?

boreal star
#

Yes

rotund hornet
#

Yeah and the range of arccos is 0,pi

boreal star
#

Yes

rotund hornet
#

So then what?

boreal star
#

Yeah so the range is [0,2pi]

rotund hornet
#

So you multiplied them?

boreal star
#

Yes

rotund hornet
boreal star
#

No

#

That was domain

rotund hornet
#

Why can you multiply for range but not domain?

boreal star
#

What is domain?

rotund hornet
#

The possible x values

boreal star
#

Basically the domain of a function is the set of values the input of the function can take so that the function returns a value in the codomain.

#

Here, the domain is the set of values of x such that the function gives real values. If I multiply the function by any real number (but 0), it does not affect the domain, as I can still take the same values of x and get a real output from the function

#

On the other hand, range is the set of values that the function returns from the argument. So if I'm multiplying a real number to the function, it changes the range of the function.

rotund hornet
#

Ohhhhhhhh

#

Understood

rotund hornet
boreal star
#

No. See we need the range of y=2arccos(sin x), the range of sin x is [-1,1], so y ranges from 2arccos(-1) to 2arccos(1), right? Now since the domain of arccos is [-1,1], [arccos(-1),arccos(1)] is the range of arccos, which is [0,pi], so 2arccos(-1) to 2arccos(1) would be [0,2pi]

rotund hornet
boreal star
#

It does not give me the same thing. If the range of y is [a,b], then what should be the range of 2y?

rotund hornet
#

2a,2b

rotund hornet
#

Multiplying it by -1,1 gives the same thing

boreal star
#

Why would you multiply it with -1 or 1?

rotund hornet
#

Wait nvmmm

#

I get it

#

Thank you so much

#

.close

vocal sleetBOT
#
Channel closed

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#
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hearty delta
#

Hi, I need help with this problem, not the answer jsut an explanation to what it is asking:

hearty delta
#

is the boundary just the highest/lowest c values on the map or?

vocal sleetBOT
#

@hearty delta Has your question been resolved?

vocal sleetBOT
#
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vocal sleetBOT
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elfin moon
vocal sleetBOT
vocal sleetBOT
#

@elfin moon Has your question been resolved?

blissful saffron
#

open a complex analysis textbook

elfin moon
#

.close

vocal sleetBOT
#
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trim walrus
vocal sleetBOT
trim walrus
#

How do you get started with

paper depot
#

so A = ds(4444^4444), B = ds(A), and we're asked for ds(B), where ds stands for digit-sum.

trim walrus
#

Yes

paper depot
#

in other words we're asked for ds(ds(ds(4444^4444)))

#

about how many digits do you expect 4444^4444 to have?

trim walrus
#

I mean like how am I suppose ans that

#

They are finite

#

But idk how many

paper depot
#

well, what happens to the digit length of a number when, say, you square it?

#

roughly

trim walrus
#

They double there self

#

But there are expectations perhaps like 2²=4, 3³= 9??

paper depot
#

did you mean "expectations" or did you fall victim to autocorrect

trim walrus
#

Exception

paper depot
#

ok you fell victim to autocorrect

#

anyway, your wording of "They double there self" is clunky, but yes. the digit length approximately doubles.

#

n^2 is certainly not more than twice as long as n itself.

#

what do you think would happen to a number's length if you raised it to the 4444th power?

trim walrus
#

Well, like if you square then the lengths double then might be that if you raise it to 4444th Power the length might be x4444

paper depot
#

yes

#

so about how many digits would you expect 4444^4444 to have?

trim walrus
#

Ummm to have 4444 digits

#

Roughly

paper depot
#

are you sure

#

or are you not reading the things you yourself are saying

#

raising to the 4444th power multiplies the length of the number (roughly!) by 4444,
but what is the length of 4444 itself? certainly not 1!

trim walrus
#

Alr I get it

#

4×4444

paper depot
#

yes

#

and this is a rough estimate, but it'll be enough for us.

trim walrus
#

but we only know the length not the digits ....

paper depot
#

our gigantic power has, let's say, at most 18,000 digits.

trim walrus
#

Alr

paper depot
#

and while we do not know exactly what those digits are,

#

this info still lets us put an upper bound on ds(4444^4444).

#

do you see how or should i prompt you further?

trim walrus
#

Ahhhh.....NO

#

I don't see it

#

Guide me ....

paper depot
#

what's the biggest that one individual digit can be?

trim walrus
#

9

paper depot
#

so with a number 18000 digits long, at most how big can its digit sum be?

trim walrus
#

9×18000

paper depot
#

exactly

trim walrus
#

That's it??

paper depot
#

no, that's not yet it.

#

but we know A = ds(4444^4444) ≤ 162000.

#

this means A is at most a 6-digit number starting with a one.

#

that severely limits what ds(A) could be !

trim walrus
paper depot
#

A = ds(4444^4444) ≤ 162000.

#

A ≤ 162000

#

do you understand this or not

trim walrus
#

Yes I certainly do, but how does that and that relate??

paper depot
#

if A ≤ 162000, can A be longer than 6 digits?

trim walrus
#

Yep, I'm dumb

#

Alr

#

So, ds(4444^4444) can't be longer than

#

6

merry python
#

IMO 1975 Problem 4

trim walrus
paper depot
#

ds(4444^4444) can't be longer than 6 digits

trim walrus
#

Alr

paper depot
#

so what's the biggest that ds(ds(4444^4444)) could be, given this?

trim walrus
#

Welll, as ds(4444^4444) can't be greater than 6, the atmost level the max number will be 999999 ds(999999)....

#

Ap 9×6 = 56

paper depot
#

9*6 is not 56

trim walrus
#

54

#

F

paper depot
#

also we can do a bit better than that, since not all six-digit numbers are available as values for A

#

but i suppose that actually doesn't matter.

#

so B ≤ 54 now

merry python
paper depot
#

as ds(4444^4444) can't be greater than 6
this is incorrect as written btw

trim walrus
#

Why is that so??

paper depot
trim walrus
#

Hmm

#

Alr

#

ds(199999) = 1+9×5 = 46

#

B <= 46

paper depot
#

yeah, ok

trim walrus
#

We need to find ds(B)

paper depot
#

now find an upper bound for ds(B)

merry python
#

apply the same thing again
First digit will be 4 and two digit number

paper depot
#

we won't be done even after finding it, however.

trim walrus
#

So B =< 42, it can't be greater than 2 (length) so at peak it has to be 42 again??

merry python
#

how 42?

#

the length must be two and first digit must be 4

#

so the max you can have is 49

#

find its ds

paper depot
#

39, actually.

#

no number between 40 and 42 can beat 39's digit sum

merry python
trim walrus
#

49

merry python
#

okay so what is its digit sum

trim walrus
#

13

merry python
#

So we're now done with the first part
Now are you aware of modulo?

trim walrus
#

Yes but

#

Wait

paper depot
#

yes? is there something wrong?

trim walrus
#

B <= 42, so it as to be a smaller number less than 42 and should have two digits so how's 42 not correct??

paper depot
#

are you asking why B ≤ 42 doesn't mean ds(B) ≤ ds(42)?

trim walrus
#

I mean it is 2 digit long

merry python
trim walrus
paper depot
#

can A be 2##### or 3##### or 4##### etc.?

trim walrus
#

No, but A can be 161999??

paper depot
trim walrus
#

Yes

#

And be 162000 at its peak

#

It can't go beyond that

#

But here B <= 42, how's 49 coming up??

paper depot
#

we're looking at the biggest digit sum possible among the numbers 1, 2, 3, ..., 42

#

and saying that none of them have digit sum greater than 4 (max value of tens digit) + 9 (max value of units digit)

merry python
trim walrus
#

Yes

paper depot
#

do you wish to argue AGAINST any part of my argument?

#

yes or no

trim walrus
#

No

#

Alr we'll continue

#

So we get 39 as per I understand

paper depot
#

"we get 39" is vague

#

we get that ds(B) ≤ 12.

trim walrus
#

Alr

#

Yes

paper depot
#

now consider

#

for ANY natural number n, it is true that ds(n) ≡ n (mod 9)

#

do you understand this or not

trim walrus
#

I understand that 9 | ds(n) - n

paper depot
#

should i read this as "I understand that 9 | ds(n) - n, but not ds(n) ≡ n (mod 9)"?

#

yes or no

trim walrus
#

No

#

I understand both

#

I understand what you're saying

#

It is true

paper depot
#

why not just say "yes"

#

saves effort for both you and me

trim walrus
#

Alr alr

paper depot
#

anyway, applying this three times, we get that ds(B) has the same remainder mod 9 as that big power we started with, 4444^4444

#

are you able to find the remainder of 4444^4444 mod 9?

trim walrus
#

0

merry python
#

No

trim walrus
#

1

#

Alr

merry python
#

Are you just guessing

paper depot
trim walrus
paper depot
#

i mean there are finitely many options

#

basudev, you should give straight answers to yes/no questions that people ask you

#

right now you AVOIDED that

#

and instead started guessing

#

i find that extremely annoying

#

please do not do this ever again

merry python
#

first of all find remainder of 4444 mod 9

trim walrus
#

Alr

#

9×493+smth= 4444
smth = 4444-9×493

#

7??

merry python
#

well 7 is right

#

Now try to find remainder of what power of 7 mod 9 is one

trim walrus
#

Leaves a remainder of 0, so

#

??

paper depot
#

WHAT leaves a remainder of 0?

trim walrus
#

Fuck shake dude 9-7= 2

#

2^x = 1

#

X=0

#

0000000

#

Alr I got it

merry python
paper depot
#

i think you in fact did not get it.

paper depot
merry python
#

oh shi-

#

rem 1 is what I meant

#

Okay I'm out. Better let Ann help

paper depot
#

i'm having trouble helping actually

trim walrus
#

Alr I'll figure it out

#

Myself

#

Thanks for the help

#

.close

vocal sleetBOT
#
Channel closed

Closed by @trim walrus

Use .reopen if this was a mistake.

vocal sleetBOT
#
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mint iris
#

Hello, can anyone help out with this question (e) . I tried using the pq formula, but could not get to a suitsble answer

mint iris
#

.help

vocal sleetBOT
#

Commands:
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help: .help

Type .help <command name> for more info on a command.

outer warren
#

pq formula is overkill for that,
still show us how you tried to apply that

mint iris
#

.I can show

#

everything above Retry

#

Is what I have done

outer warren
#

you're using the wrong p value

#

p is the coefficient of x,
which is 14, not 7

mint iris
#

I get it

#

I will try and inform if i stuck

#

There is the answer I think

#

I have got it right, thanks for helping out

#

.close

vocal sleetBOT
#
Channel closed

Closed by @mint iris

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vocal sleetBOT
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celest kite
#

Im stuck in this question please help.

vocal sleetBOT
celest kite
#

I try writing a system of equations then use a matrix that represents the system and perform row operations until the matrix is in echeleon form. However, I seem to do something wrong in the process

vast shale
#

-96 = a(-3)^3 +b(-3)^2 +c(-3) +d -2 = a(-1)^3 + b(-1)^2 +c(-1) +d 4=a(1)^3 + b(1)^2 +c(1) +d 19=a(2)^3 +b(2)^2 +c(2)+d then you solve this system of 4 equations to find the values of a,b,c and d

#

oh show me how you did it

celest kite
#

Too many steps but. I started with this

#

Not a neat handwriting sorry

vast shale
#

don't worry

celest kite
#

Then I interchange rows 1 and 3

#

From the matrix

#

Then I did operations to perform row operations that make 0 appear below in column 1

#

R2=r1+r2

#

Beginning with that

karmic imp
#

If you added the two, you just have b and d left

celest kite
#

But what about the -2 and 4 on the other side

karmic imp
#

I'm saying the left side would be much easier to simplify since you have zeros

celest kite
karmic imp
#

I never said 0 = 2

#

I said you can add up R2 and R3

dreamy viper
#

yes^

#

0s so you add less in columns 1 and 3

karmic imp
#

If you noticed how in R2 and R3, the a and c terms have equal coefficients but are opposite

#

So they would cancel out

dreamy viper
#

then interchange R3 and R1 if you haven't

vocal sleetBOT
#

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

vast shale
#

welp

#

I'm stupid

karmic imp
#

You want to end up with a upper triangular matrix

celest kite
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Not really I got started. I can follow steps given but understanding not really. I just started learning echelon form

karmic imp
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Since you are new to echelon, I suggest this video
https://www.youtube.com/watch?v=eDb6iugi6Uk&ab_channel=TheOrganicChemistryTutor
And I suggest working with smaller matrices at first, to get the hang of it before going into a 4x4 and bigger as it takes more algebra

This precalculus video tutorial provides a basic introduction into the gaussian elimination - a process that involves elementary row operations with 3x3 matrices which allows you to solve a system of linear equations with 3 variables. You need to convert the system of equations into an augmented matrix and use matrix row operations to write it ...

▶ Play video
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This precalculus video tutorial provides a basic introduction into the gaussian elimination with 4 variables using elementary row operations with 4x4 matrices. You need to convert the system of linear equations into an augmented matrix and write it row echelon form using matrix row operations. You can solve the system using back substitution. ...

▶ Play video
dreamy viper
celest kite
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Thanks!
I think for the problem I have to interchange row 1 and 3. Then R2=r1+r2 next R3=27r1+r3 but if there is an easier way...

karmic imp
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Overall, you have slightly bigger numbers so it's going to take time

celest kite
karmic imp
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Just take your time with the math

vocal sleetBOT
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@celest kite Has your question been resolved?

celest kite
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I finally got it for R3=27r1+r3 I incorrectly did 27(1)-96 instead of 27(4)-96 thats I was off.

karmic imp
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Fyi you should react to the bot's message so the channel doesn't close

karmic imp
vocal sleetBOT
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Channel closed

Closed by @celest kite

Use .reopen if this was a mistake.

karmic imp
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.reopen

vocal sleetBOT
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celest kite
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Its chicken scratch

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right now

karmic imp
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Were you done with the channel? Because the check means you are done and it closes the channel

celest kite
karmic imp
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If you got the answer, then what did you mean by

I finally got it for R3=27r1+r3 I incorrectly did 27(1)-96 instead of 27(4)-96 thats I was off.

celest kite
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I was explaining why I wasn't getting it correctly I was doing the row operations and accidentally put a 1 instead of a 4

karmic imp
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Alright since you're done with the channel, I'll close it

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.close

vocal sleetBOT
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Channel closed

Closed by @karmic imp

Use .reopen if this was a mistake.

karmic imp
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If you want you can dm the work, still

vocal sleetBOT
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warm atlas
#

Hello, I might just be doing this wrong but the answers for angle A don't match up (which is underlined in red). I have looked over it but I can't seem to find what I've gotten wrong. It could also be that the answer for BC was wrong.. (Calculator was used btw)

vocal sleetBOT
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@warm atlas Has your question been resolved?

warm atlas
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<@&286206848099549185>

wraith python
warm atlas
#

Ah damn, I see. Tyvm.

#

.close

vocal sleetBOT
#
Channel closed

Closed by @warm atlas

Use .reopen if this was a mistake.

vocal sleetBOT
#
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.

spring gate
vocal sleetBOT
spring gate
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i understand everything here

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exept where that 1/4 came from?

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am i being dumb and just missing something?

urban edge
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Substitute du/4 for dx

last creek
vast shale
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^^^

spring gate
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um... ok but why does dx = 1/4?

last creek
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and not 1/4

spring gate
last creek
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u have to substitute du / 4 in place of dx

spring gate
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but both are in the same line?

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int (4x-3)^3 dx

last creek
spring gate
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where are they getting du = 1 then?

last creek
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where are they getting du = 1 ?

spring gate
last creek
spring gate
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im really not following this at all

last creek
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that's int u^3 du/4

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u can take the constant term out of the integral

spring gate
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what constant?

last creek
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1/4

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1/4 is a constant value

spring gate
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so the 1/4 comes from the (4x-3)

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?

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its taken from there

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right?

last creek
# spring gate

read each line thoroughly
they are explaining everything

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if u substitute something u have to find a relation as well

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as in this example we substituted 3x+4 as u

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but can't solve $\int u^5 dx$

spring gate
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substitution seems so pointless

twin meteorBOT
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_kapp_

last creek
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so we need to find the relation between du and dx

spring gate
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(ax-c)^b = 1/a*(ax-c)^b+1/b+1

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is that formula correct in terms of integration

last creek
spring gate
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2/ what

last creek
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can u write in latex or on a notebook and send me a picture

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Usually the method of integration by substitution is extremely useful when we make a substitution for a function whose derivative is also present in the integrand. Doing so, the function simplifies and then the basic formulas of integration can be used to integrate the function.

spring gate
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ignore the qudratic at the top

last creek
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seems correct to me

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but as i said above

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substitution in general is better than memorising so many results

spring gate
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ok so

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all im hearing is that its a better meathod for advanced stuff

last creek
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yes

spring gate
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but rn its just overcomplicating simple formula

spring gate
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why does "du/dx" = 4

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d(4x-3) / dx