#help-26

1 messages · Page 43 of 1

jade thunder
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we just showed the right side

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if i stick the right side one in here

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i get this

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so there's 2 maxes going on

opal vault
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$\forall x\in \bR^n, |x| < 1$, $|\partial^\alpha\varphi(x)| \leq \frac{2^{d/2}\sup_{|x'|<1}|\partial^\alpha\varphi(x')|}{(1+|x|^2)^{d/2}} \leq \frac{C_{d,\alpha}}{(1+|x|^2)^{d/2}}$

thorny flameBOT
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rafilou2003

jade thunder
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what happened to the 2^d/2 for the C_d,alpha

opal vault
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definition of C d alpha

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it's bigger than the term on the right

jade thunder
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oh it's inside

jade thunder
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we have C_d,alpha = max(p*, 2^d/2 thing)

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and p* = max(thing1, thing2)

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so we have 2 maxes going on

opal vault
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C and Cdalpha are different, remember that

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$C = \sup_{|x'|<1}|\partial^\alpha\varphi(x')|$

thorny flameBOT
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rafilou2003

opal vault
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it's this C here

jade thunder
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what's the '

opal vault
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so we use a different dummy variable

opal vault
jade thunder
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ah it's just used to descibred the furthest (\partial^\beta \varphi(x)) can take us

thorny flameBOT
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Frosst

jade thunder
opal vault
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yes

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the furthest it can take us inside the unit ball

jade thunder
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right it's not really a varaible since we take hte sup of that

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so really there's only "1" value that gives us the sup

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or maybe a bunch of them that gives the same sup either way

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it's not a variable

opal vault
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yes

jade thunder
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well i suppose it depends on varphi and beta

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but that's not the point here

jade thunder
opal vault
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So for $|x|<1$, $|\partial^\alpha\varphi(x)| \leq C$

thorny flameBOT
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rafilou2003

opal vault
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by definition of sup, right?

jade thunder
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true

opal vault
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but we showed this

jade thunder
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ah

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that's also true

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so you bound that C by the thing on the right

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with another C

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that's indeed true again

jade thunder
opal vault
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yes

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And finally, by definition of Cdalpha

jade thunder
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and that in turn is yet smaller than the C_d, alpha

opal vault
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the numerator is smaller than Cdalpha

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by its definition

jade thunder
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ah

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because it is at leas thte same as the middle term

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because if that was the biggest we'd have pikcedi t

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if p* was bigger then of course it's bigger

opal vault
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$b\leq \max(a,b)$

thorny flameBOT
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rafilou2003

jade thunder
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indeed

opal vault
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so giving us the final inequality

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$\forall x\in \bR^n, |x| < 1$, $|\partial^\alpha\varphi(x)| \leq \frac{C_{d,\alpha}}{(1+|x|^2)^{d/2}}$

jade thunder
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but that's only for |x| < 1

opal vault
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Yes, now we need to prove it for |x| >=1

jade thunder
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oh dear

thorny flameBOT
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rafilou2003

jade thunder
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that's a lot of steps they've hidden in 1 line

opal vault
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For $|x| \geq 1$, we know by definition that $|x|^d|\partial^\alpha\varphi(x)|\leq p^*_{d,\alpha}(\varphi)$ right?

thorny flameBOT
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rafilou2003

opal vault
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definition of supremum

jade thunder
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from here?

opal vault
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well yes

jade thunder
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oh that's the wrong one

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this one

opal vault
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yes

opal vault
jade thunder
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what happens

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then |x| >=1 is bounded by the same bound as for |x| < 1

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ok that makes sense

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that would be like the e^-x^2 example

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the overall upper bound is in |x| < 1 and for |x| > 1 it's still bounded by the upper bound of |x| < 1

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ok now if the right one is bigger

jade thunder
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either we took the left one and p* is bigger

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or we take the right one and we are at equality

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ok good

opal vault
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all good?

jade thunder
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yes

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good

jade thunder
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so now we have $|\partial^\alpha\varphi(x)|\leq \frac{p_{d,\alpha}^*(\varphi)}{|x|^d}$

thorny flameBOT
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Frosst

opal vault
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so now we just need to find a constant to bring us back to the denominator we want

jade thunder
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hmm

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i see what you mean

opal vault
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ah I think we need 2^d/2 again maybe

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no doesn't work

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Ah I got it

jade thunder
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but we wanna make the left side still big right

jade thunder
opal vault
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Now $1\leq |x|$ right?

thorny flameBOT
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rafilou2003

jade thunder
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that is true

opal vault
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So $(1+|x|^2)^{d/2} \leq 2^{d/2}|x|^d$

thorny flameBOT
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rafilou2003

jade thunder
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is that from before

opal vault
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yeah but we need to change it because |x| >= 1

jade thunder
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so we had this

opal vault
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$1+|x|^2 \leq 2|x|^2$, is that alright?

thorny flameBOT
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rafilou2003

jade thunder
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now you multiply it but something thats > 1 on the right

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true

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that inequality will still hold

opal vault
jade thunder
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wait does that work

opal vault
jade thunder
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no it doesnt

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hold up

opal vault
jade thunder
opal vault
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yes

jade thunder
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ok sure

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we added |x|^2 to both sides

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now we raise both sides to d/2

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ah

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that is indeed true

opal vault
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ok good

jade thunder
opal vault
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So uh I didn't anticipate this but I'll have to change Cdalpha a bit

jade thunder
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will it change the stuff from before?

opal vault
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$C_{d,\alpha} = \max(2^{d/2}p^*{d,\alpha}(\varphi),2^{d/2}\sup{|x|<1}|\partial^\alpha\varphi(x)|)$

thorny flameBOT
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rafilou2003

opal vault
jade thunder
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ah

opal vault
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and we used the right term on what we did before

jade thunder
opal vault
thorny flameBOT
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rafilou2003

jade thunder
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then we sub that in for the denominator

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uh huh

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very clever

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$|\partial^\alpha\varphi(x)|\leq \frac{p_{d,\alpha}^(\varphi)}{|x|^d} \leq \frac{p_{d,\alpha}^(\varphi)}{\frac{(1+|x|^2)^{d/2}}{2^{d/2}}}$

thorny flameBOT
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Frosst

jade thunder
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so we have this now

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$|\partial^\alpha\varphi(x)|\leq \frac{p{d,\alpha}^(\varphi)}{|x|^d} \leq \frac{2^{d/2}p_{d,\alpha}^(\varphi)}{(1+|x|^2)^{d/2}}$

thorny flameBOT
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Frosst

jade thunder
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aha

opal vault
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yep that's good enough

jade thunder
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that's the other part of our C_d,alpha

opal vault
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So $\forall x\in \bR^n, |x| \geq 1$, $|\partial^\alpha\varphi(x)| \leq \frac{C_{d,\alpha}}{(1+|x|^2)^{d/2}}$

thorny flameBOT
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rafilou2003

jade thunder
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and also for |x|< 1

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so then it's just for all x

opal vault
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done

jade thunder
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that is a lot of stuff

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well, the other guy did hope i could get to page 3

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alright thank you so much for your patience

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i will look through this again in the morning

opal vault
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good luck

jade thunder
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.close

topaz sinewBOT
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ruby torrent
topaz sinewBOT
ruby torrent
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answer

fast yarrow
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A looks like simple multiplication since 3000 every year, so total money is 3000×7. 7yr for 19 to 25th birthday

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B is Geometric progression with
a = 400
r = 2
Sum of Geometric B= a(r^n-1)/(r-1) i think

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And tabular form smth like this probably

topaz sinewBOT
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@ruby torrent Has your question been resolved?

ruby torrent
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I did this for option A

topaz sinewBOT
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@ruby torrent Has your question been resolved?

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proud smelt
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I need help in finding the domain of this function

proud smelt
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y=(x^2-x-2)^-1

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Idk what to do in order to find the domain

acoustic tangle
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You just need to make sure that x^2 - x - 2 is not equal to 0 as 0^-1 is undefined (Assuming you are asked to find the maximal domain within reals)

proud smelt
acoustic tangle
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Yeah

proud smelt
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but I don't understand why it can't be equal to 0

acoustic tangle
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Because 0^-1 is undefined

proud smelt
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oh

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I just realized

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thanks man

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potent terrace
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|x-3| < 2|x|
how do i solve this linear inequality? do i first divide by x to get it to the other side?

hallow depot
topaz sinewBOT
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@potent terrace Has your question been resolved?

topaz sinewBOT
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slender smelt
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Hello there, I'd like to know what is the procedure to getting the inverse function of f(x)= 1/x+2, which is (1/x)-2

long stirrup
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it's not the correct reverse

acoustic tangle
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You mean $\frac1{x+2}$?

slender smelt
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for real?

thorny flameBOT
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A Lonely Bean

slender smelt
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yes

acoustic tangle
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You should have used parenthesis there then lol

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1/(x + 2)

long stirrup
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ah ok

slender smelt
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my bad

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is it possible to move 2 out of the division by changing its sign to negative?

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sadly, no

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english isn't my native language so I'm not very familiar with terminology in english

slender smelt
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you mean to say that the inverse of x+2 is y-2?

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I'm starting to think I wasn't taught how to get inverse functions properly, or that there is something I don't know about reciprocal functions

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As i was taught, you start by expressing the function as y = 1/(x+2)

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and when you get the inverse, you swap y with x

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I'm more curious about how 2 is out of the division in the inverse, and I don't see how swapping x with y explains how the 2 is changed

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ok, I understand that, what I don't understand is how 2 is adding to x in the division on f(x) but on the inverse it's outside of the division

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the problem is more related to algebra here I think

thorny flameBOT
slender smelt
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each day I realize how blind I can be from seeing things

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I was brainstorming on this for hours yesterday

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not really

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for like an hour and a half prob

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but damn do I suck at algebra

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Yea, don't know how to thank you

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sorry for any annoyance

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placid valley
#

Guys, I have a confusion. in a complex number of the form: a+bi. a is the real part and b is the imaginary part, however b is not an imaginary number(when squared will produce a negative) b is a real number what makes it imaginary is i. So why do we refer to be as the imaginary part? Why do we not consider the imaginary part as bi because b itself is not an imaginary number. Or am I wrong?

placid valley
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I think you meant to write in a help channel rather than an already existing channel for me

hallow depot
placid valley
hallow depot
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no

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no idris he talked about imaginary number not complex

placid valley
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yeah but b is a real number, then why do we call it the imaginary part?

odd pagoda
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we just call it imaginary part because it is in front of the i

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its not supposed to be imaginary itself

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in fact its nice that it is real because then we can treat it like we can treat any real number

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no

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just b

placid valley
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I'm saying that only i is imaginary, b is real so why do we refer to is specifically "imaginary part"

odd pagoda
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because names

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what do you want to hear

hallow depot
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its the definition !

odd pagoda
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I can also call it orange part but that would be an even worse name

hallow depot
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gabe if you want b immaginary then immaginary part of -1=i*i would be i ...that doesn t make sense

placid valley
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yeah that's fair enough, I was just confused that whether b is an imaginary number itself

odd pagoda
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no. b is the imaginary part

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thats the whole point of why gabe is asking

placid valley
odd pagoda
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because it is attached to the i

placid valley
# odd pagoda because it is attached to the i

hmm yeah that make sense, i was only confused by the fact that whether b is an imaginary number, but as it turns out it is a real number but considered as the "imaginary part" of the complex number only because it is the coefficient of an imaginary number.

hallow depot
#

chatgpt best math teacher ,,,

odd pagoda
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!nogpt

topaz sinewBOT
#

Please do not trust ChatGPT or similar AI tools for mathematical tasks, as they often generate output which "sounds correct" but has numerous factual or logical errors. Use of these AI tools to answer other people's help questions is strictly against server rules (see #rules).

placid valley
odd pagoda
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well specifically it is the coefficient of i

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like if you had a+b*(2i) then the imaginary part would be 2b

placid valley
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I was just stupidly thought that imaginary part=imaginary number, which made this whole confusion but now it's clear

placid valley
hallow depot
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i was ironic

placid valley
hallow depot
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an ironic statement

placid valley
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"dog"?

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wow, I never would have guessed that you use an animal to describe that something is bad.

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Anyway thanks guys for your help, I appreciate it

hallow depot
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it s an insult

odd pagoda
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which is definitely totally related to the animal

hallow depot
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greatest of all time?

placid valley
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I've never heard anyone saying: "you are dog at maths" or smth

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Its def not Irish 😄 I'd guess its american

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ohh 😄

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well speaking for Ireland I've never heard anyone saying it

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ohh so thats why I never heard it then 😄

topaz sinewBOT
#

@placid valley Has your question been resolved?

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topaz panther
#

I need help

topaz sinewBOT
topaz panther
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This is where Im stuck, cant seem to match the left hand side with right hand side

hallow depot
#

induction?

topaz panther
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Yeah

hallow depot
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wow beautiful sigma symbol

topaz panther
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Haha thanks

hallow depot
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ok got it

topaz panther
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Im stressed ok

drifting swift
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yeah it's a bit too wide imo

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it looks like you traced it with a ruler

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anyway lets see whats up

topaz panther
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I dont know if Ive done the steps incorrectly or if IM just too dumb to see the answer

drifting swift
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some typographical alignment issues here

hallow depot
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$\sum_{k=0}^{n-1}(k+2)2^{k+1}=n2^{n-1}+\sum_{k=0}^{n-2}(k+2)2^{k+1}$ right?

drifting swift
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ok so uh

thorny flameBOT
drifting swift
#

lets just rewrite this into a more manageable form

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$\sum_{k=0}^n (k+2) \cdot 2^{k+1} = (n+1) \cdot 2^{n+2}$ by the looks of it

thorny flameBOT
#

AnnGhost

topaz panther
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So that part is p-2 right hand side + p-1 left hand side

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should equal to p-1 right hand side

drifting swift
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we want to show $(p-2) \cdot 2^{p-1} - (p-3) \cdot 2^{p-2} = (p+1) \cdot 2^p$ by the looks of it

thorny flameBOT
#

AnnGhost

drifting swift
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unless i fucked up

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which i could've

topaz panther
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That doesnt look right

drifting swift
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really evil of them to run the sum to n-2, ngl.

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such a minefield for fuckups.

topaz panther
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Yeah I know, first time Ive stumbled upon one

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But I assume that if the sum equals to p-2 for an example during the assuming part, all N = to p-2

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Is that correct?

topaz sinewBOT
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@topaz panther Has your question been resolved?

topaz panther
#

Nein

obsidian moth
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Have you tried induction?

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If that's what you were doing in the paper you sent please forgive. You can use your induction hypothesis to substitute the left-hand-side for the right-hand-sight when you do the inductive step, and then simplify from there

topaz sinewBOT
#

@topaz panther Has your question been resolved?

topaz sinewBOT
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median zenith
#

yo

topaz sinewBOT
median zenith
#

how do you go about calculating the edge of a graph that has an edge like where the equation has a root in it

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for example here

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and this being the formula

quartz flax
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find the point where the value under the root becomes negative

median zenith
#

basically what are the coords

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ohhh right

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domain

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soo here that would be

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-2x^2 = -12

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x^2 = 6

quartz flax
#

yes

median zenith
#

right

#

.close

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vast juniper
#

Can i get help on this question:

topaz sinewBOT
#

Please don't occupy multiple help channels.

proper lily
#

oo this is fun

vast juniper
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can i carry on here

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I'm getting that its 1/n^p * 1 * 2 * 3 ... * n-1 * n

proper lily
#

let's look at an example term

vast juniper
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but as n tends to infinity, 1 / n^p tends to zero but n! tends to infinity

proper lily
#

no clue what youre writing... id need latex visual

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but lets look at the term n = 5

vast juniper
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i know it diverges

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but i dont know how to show it

proper lily
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ah

vast juniper
#

because the numerator tends to infinity at a faster pace than the denominator tends to infinity

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so it goes to infinity but that is a very short explanation

proper lily
#

indeed, I'm thinking of a good way to show it

north spruce
#

the factorial term can have a growing number of factors

proper lily
#

id say showing that it monotonically increases is sufficient

north spruce
#

while the n^p term has only ever p factors

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so, at a point in the sequence when n! has more than p factors which are all ~n in size, then the numerator will grow faster

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as it will have a higher degree in n

vast juniper
vast juniper
proper lily
#

possible but a lot of work

north spruce
#

in particular, if look at a factorial n(n-1)(n-2)...(3)(2)(1), we can always truncate to get a strictly smaller number

north spruce
#

so, as long as n is larger than 6

hallow depot
#

diverges

vast juniper
#

factorial is basically unlimited whereas n^p is limited right

vast juniper
north spruce
# vast juniper why 6 tho?

we then can write out the first terms we can write as (n)(n-1)(n-2)(n-3)(n-4)(n-5) of our sequence and it will be smaller than n!

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so in particular, n! is larger than a 6th degree polynomial

vast juniper
north spruce
#

thats just with 6 as an example

hallow depot
#

$\frac{n!}{n^p}=\frac{n}{n}\frac{n-1}{n}...\frac{n-p+1}{n}\frac{(n-p)!}{1}$

thorny flameBOT
north spruce
#

you could instead choose larger than p

hallow depot
#

the first p terms goes to 1

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the last one diverges

vast juniper
north spruce
#

so the limit would go to infinity

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It's pretty cool! it shows that n! grows faster than ANY polynomial in n

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at least asymptotically

vast juniper
north spruce
hallow depot
north spruce
#

In general we have a heirarchy of polynomial< exponential like (2^n or 3^n) < (n!) < (n^n)

vast juniper
# hallow depot

i dont understand how you have formed the terms above the fraction, is n! = n * n-1 * ... * (n-p+1) * (n-p)! ?

hallow depot
#

n! is by definition n(n-1)(n-2)...(2)1

vast juniper
hallow depot
#

now I expanded only the first p terms

north spruce
hallow depot
#

now its more like small o

vast juniper
#

Thank you all for helping, i believe Ive got a good explanation now. I appreciate all the help!

#

what does that f emoji mean lol?

#

nvm now ive got to get back to work. Special thanks to @north spruce for explaining the concepts thoroughly!

#

.close

topaz sinewBOT
#
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lyric mountain
topaz sinewBOT
hallow depot
#

what a pen!

lyric mountain
#

I'm trying to isolate y. Is there a natural log rule I'm forgetting?

acoustic pecan
#

$e^{ln(x)}=x$

thorny flameBOT
#

AℤØ

hallow depot
#

so y(x)=kx

acoustic pecan
#

huh

#

oh

#

yeah

lyric mountain
#

oh okay

#

So, help me recall this rule. If I multipy both sides by e, would I be able to rewrite it as e^ln(y) = e^(ln(x) ) + e^C

vast juniper
#

e^ln(y) = e^(ln(x) ) * e^C (times e^C)

#

then y = x * e^C but since e^c is just a constant you can write y = x * A => y = Ax

lyric mountain
#

e^c is a constant and I follow that part

acoustic pecan
#

youre not multiplying by e

lyric mountain
#

we usually replace it with k

#

no?

#

oh wait

acoustic pecan
#

no, youre making each side an exponent of e

lyric mountain
#

yeah

#

so it's;
y = x + e^c?

#

right?

acoustic pecan
#

$$e^{ln(y)}=e^{ln(x)+c}$$

lyric mountain
#

o

#

o

thorny flameBOT
#

AℤØ

acoustic pecan
#

you can split the right side by the fact x^a * x^b= x^(a+b)

lyric mountain
#

I can rewrite this as
y = e^ln(x) * e^c tho

#

right?

acoustic pecan
#

no

#

how would that work

lyric mountain
#

why not

vast juniper
acoustic pecan
#

thats like saying if i have 5=3+2 then 2^5=2^3+2^2, 32=8+4

lyric mountain
#

is it correct now then?

acoustic pecan
#

just simplify

#

and replace the constant with some simpler notation if you want

lyric mountain
#

k!

#

I will use K!

#

Stewarts book uses k

#

so it's y = xk!

#

ughhhhh math is so much nicer when it's not for hw

#

ty ty both

#

.close

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gritty matrix
#

I'm confused on this

topaz sinewBOT
gritty matrix
#

the teacher explained us and I understood most, but the things underlined in cyan

#

is what's confusing me

#

like how did the teacher get those variables

acoustic pecan
#

the shortest distance between a point and a line, is the length of line (perpendicular to the main line) that joins them

#

the slope of the main line is 1

#

so the slope of our joining line is -1 since theyre perpendicular

#

(main line is y=x, joining line is CP)

gritty matrix
#

or only for this question?

acoustic pecan
#

not necessarily no

#

but the product of the slopes will always be -1

#

like if the main line was y=1/2 x, the slope of the joining line would be -2

gritty matrix
#

yes you filp it

#

how did they know its 1?

#

I know after it got flipped which = -1

acoustic pecan
#

y=x, y=1*x

#

m=1

autumn mica
# gritty matrix

y = -x - 2 the teacher wanted a line that's at a right angle perpendicular to y=x so they flipped the slope to -1 but when they plugged in the point (5.5,1.5) to get the equation they made a mistake It should be y = -x + 7 not y = -x - 2

#

'b' is where the line crosses the y-axis and the teacher was trying to find it but got it wrong for the point (5.5 1.5) b should be 7 not 6

acoustic pecan
#

its (-3,5), not 5.5
y-1.5=-(x--3.5)
y-1.5=-x-3.5
y=-x-2

gritty matrix
acoustic pecan
#

im just saying the teachers work is fine

#

anyway

gritty matrix
#

so the y= -x + 7?

acoustic pecan
#

the slope was from the fact the main line is y=x, so the slope is 1

acoustic pecan
gritty matrix
#

or was the teachers work correct

acoustic pecan
#

it is y=-x-2

acoustic pecan
#

they were mistaken

gritty matrix
#

ohh

#

ok

acoustic pecan
#

they read the point C wrong

gritty matrix
#

and this

#

the underlined cyan

#

where did they get that from

acoustic pecan
#

y=x is given in the question

gritty matrix
#

ohhh

acoustic pecan
gritty matrix
#

so could I also have used elimination?

acoustic pecan
#

no?

#

oh

gritty matrix
#

or only substitution

acoustic pecan
#

you mean to find the intersection?

gritty matrix
#

could I have used elimination instead

acoustic pecan
#

if you wanted to use elimination, feel free to

gritty matrix
#

okay thanks

gritty matrix
#

ty

#

.close

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#
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neon iron
#

hi

#

part d

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neon iron
#

seems like greedy on highest urgency?

topaz sinewBOT
fluid belfry
#

?

neon iron
fluid belfry
#

oh mb

topaz sinewBOT
#

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slow tusk
topaz sinewBOT
slow tusk
#

what did they do in this step? why does 8y+2x become 4y+x

#

i know it’s divided by 2, but why?

fallow chasm
#

They multiplied both sides of the equality by 8y+2x. So it cancels out on the LHS and becomes 1/2(8y+2x) = 4y+x on the RHS.

slow tusk
#

Im stoopid

#

.close

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pearl pulsar
#

I'm trying to show that the function f:(-1,1)-> R f=x/(1-x^2) is bijective. For surjectivity, I got the quadratic equation: 1+-sqrt(1+4a^2)/2a but I'm not sure how to show that one of these is in (-1,1)

pearl pulsar
#

I'm trying to show that the function $f:(-1,1)\to\mathbb{R}, f=\frac{x}{(1-x^2)} {}$ is bijective. For surjectivity, I got the quadratic equation: ${} x=\frac{1\pm\sqrt{ (1+4a^2) }}{2a} {}$ but I'm not sure how to show that one of these is in (-1,1)

thorny flameBOT
#

Jesses

topaz sinewBOT
#

@pearl pulsar Has your question been resolved?

pearl pulsar
#

<@&286206848099549185>

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gritty mirage
topaz sinewBOT
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atomic anchor
#

Describe the sequence of rigid transformations that shows ABC is congruent to A’B’C’ ?
A (5,7), A' (-2,7)
B (0,2) , B' (3, 2)
C' (7,4), C' (1,9)

atomic anchor
#

I tried to do this but it was too difficult for me I need somebody to help me out

#

What I did was

#

I was already kinda out of ideas so I just reflected onto the y axis

#

But then I can’t translate point C correctly

#

So that idea was wrong

#

And now I’m stuck

#

Uh

#

<@&286206848099549185> sorry, could you please help me out here?

topaz sinewBOT
#

@atomic anchor Has your question been resolved?

topaz sinewBOT
#

@atomic anchor Has your question been resolved?

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#

@atomic anchor Has your question been resolved?

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molten marlin
topaz sinewBOT
molten marlin
#

can someone help me with this

#

i just started integrals

#

i dont understand how they got that'

silver trench
#

we know that the maximum value of the interval is 2

molten marlin
#

yes

silver trench
#

we dont know what the true area of under the graph of that region is

#

but we know that i cant exceed 6

molten marlin
#

why not?

#

cuz of the interval and maxvalue?

#

max value

silver trench
#

yes

molten marlin
#

2*3

silver trench
#

let me draw you a graph

molten marlin
#

?

#

alr

silver trench
#

this would be the only possible way for the area to be 6

molten marlin
#

yea

silver trench
#

is if the value of the function between 0-3 is constant (2)

molten marlin
#

oh ok makes sense

#

also

#

it cant be A or B cuz we dont know what the graph looks like and dont know if its increasing or decreasing right

#

or no?

molten marlin
#

what about C

molten marlin
silver trench
#

so we cant rule it out

molten marlin
#

oh alr

#

ty for the help

#

.close

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quaint plover
topaz sinewBOT
ornate magnet
#

What have you tried

quaint plover
#

i am clueless right now

ornate magnet
#

ζ= rF sinθ

#

rsinθ= r perpendicular

quaint plover
#

is the perpendicular 0.45m?

ornate magnet
#

Do you know this?

ornate magnet
quaint plover
#

what is the torque then?

#

nvm i have the calculate it

#

is the answer 45?

ornate magnet
#

Yes

quaint plover
#

thank you

#

.close

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limpid mica
#

trying to solve this ode with these initial conditions but im lost

limpid mica
#

this is what i got so far but idk if it is right

#

i dont think it makes sense to me because wouldnt i need to find e^pi?

sweet shard
#

,calc e^pi

thorny flameBOT
#

Result:

23.140692632779
limpid mica
#

hm

#

it still does not fit the answer (i have the key for it) im just lost on how to get to it

#

as c1 is 1, c2 os -1

#

i got c1 as 1

#

i got this

#

i am so tupid i did the derivative wrong

#

i got derivative e^x in then product rule as multiplying another e^x, for some reason

#

ty

#

.close

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neon iron
topaz sinewBOT
neon iron
#

I don't know where to start

#

i don't want the answer

#

i just don't know where to start

topaz sinewBOT
#

@neon iron Has your question been resolved?

neon iron
#

No

#

<@&286206848099549185>

magic ingot
# neon iron

you should start by writing the numers that use only th edigits 1,2,3,5 and 7

#

then look at the first 31 numbers which are divisible by 5

#

add those numbers up

#

and ur done

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#

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mortal spear
#

I think I got it, just need someone to point up my mistake

mortal spear
#

we re-writte the denominator

#

and use trig-subs

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#

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native moth
#

.solved

cosmic jackal
#

.reopen\

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barren garnet
topaz sinewBOT
sharp dew
#

is there any part of your question which makes you confused?

topaz sinewBOT
#

@barren garnet Has your question been resolved?

barren garnet
barren garnet
#

Please guide

sharp dew
#

the bottom one is quite commonly used to solve questions revolve standard deviation.

barren garnet
#

Yes. I used this formula

#

But it became complicated

#

In last term

topaz sinewBOT
#

@barren garnet Has your question been resolved?

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#

@barren garnet Has your question been resolved?

barren garnet
#

.close

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eternal spoke
#

,w plot |x|

topaz sinewBOT
thorny flameBOT
eternal spoke
#

Why does the graph have negative values

junior acorn
#

it doesnt tho

eternal spoke
#

Oh yeah im dumb

#

Thanks

#

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neon iron
#

\def \P{\mathrm P}
Does [
\map \P{\overline A \cap \overline B} = 1 - \map \P{A\cup B}
]

thorny flameBOT
neon iron
#

just a quick question

carmine marten
#

yes (by de morgan)

neon iron
#

ty

#

.close

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neon iron
#

If each coded item in a catalog begins with 2 distinct letters followed by 3 distinct nonzero digits, find the probability of randomly selecting one of these coded items with the first letter a vowel and the last digit even.

neon iron
#

i have [
\map \P A = \f{25\cdot 8 \cdot 4 \cdot 5 \cdot 4}{26 \cdot 25 \cdot 9 \cdot 8 \cdot 7}
]

#

would this be true perhaps

#

hmm

thorny flameBOT
lean meteor
#

5 x 25 x 4 x 8 x7

#

why u get 4 there

neon iron
#

yeah 7

#

typo

#

.close

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lament halo
#

.close

neon iron
topaz sinewBOT
drifting swift
#

to cut away all the extra distracting questions:

#

$x^2 - 2x - \log_2|1-x| = 3$

thorny flameBOT
#

AnnGhost

neon iron
#

Number of roots of the equation x2 – 2x – log2 | 1 – x | = 3 is

drifting swift
#

this is your equation and you want to find how many roots it has, yes?

neon iron
#

yes

drifting swift
#

ok

#

progress?

neon iron
#

umm yes

drifting swift
#

!show

topaz sinewBOT
#

Show your work, and if possible, explain where you are stuck.

neon iron
#

i dont have a phone rn

#

i can tell

#

got 3 in rhs

#

lhs*

#

then completed the square

#

then simplified a bit

drifting swift
#

and what did you end up with

neon iron
#

2^(x+1)(x-3) + x = 1 ,,,, for x <1

2^(x+1)(x-3) = x -1 ,,,,, for x >1

drifting swift
#

this is suspicious

topaz sinewBOT
#

@neon iron Has your question been resolved?

neon iron
#

?

topaz sinewBOT
#

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neon iron
#

can anyone help me with this i was absent from school when we learnt it and dont understand it

weak zealot
#

A force of 200N acts over the area of 40cm^2 calculate the pressure

#

can any one help me

craggy haven
neon iron
#

YE CANT UNDERSTAND IT

weak zealot
craggy haven
neon iron
lone nest
#

This looks more like a law of sines problem.

neon iron
#

can someone help?

topaz sinewBOT
#

@neon iron Has your question been resolved?

topaz sinewBOT
#

@neon iron Has your question been resolved?

neon iron
#

no

wicked hemlock
# neon iron can anyone help me with this i was absent from school when we learnt it and dont...

sin rule states that sinA/a = sinB/b = sinC/c, a being the length opposite to angle A. essentially it's just plugging in numbers... that would give you a basic angle (which, in this case doesn't happen to be obtuse). use the ASTC quadrants to find an obtuse value of C. the quadrants part might be a bit more difficult to understand, i'd recommend consolidating with your teacher or watching a video explanation for that

#

this is the quadrant thing i'm referring to. apologies if i'm not using the correct terminology

wicked hemlock
#

man.. im sorry

candid pilot
#

where is the question

twin linden
#

Hello?

topaz sinewBOT
#

@neon iron Has your question been resolved?

candid pilot
#

@neon iron Show us the question

neon iron
candid pilot
#

$$\frac{\sin(A)}{A} = \frac{\sin(B)}{B}$$

thorny flameBOT
#

Ratatatat

candid pilot
#

Use this to solve the problem. Remember the angle is obtuse

topaz sinewBOT
#

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toxic stirrup
topaz sinewBOT
toxic stirrup
#

i got to lim (cos(8.5/x^8)*8.5/x^8)/(-9/x^16)

#

but what do i do next

eternal wing
#

I'd say start from scratch again since that's not the correct approach

#

Have you learned about this limit?

#

$\lim_{x \to 0} \frac{\sin x}{x}$

thorny flameBOT
#

RedstonePlayz09

eternal wing
#

@toxic stirrup

toxic stirrup
#

its 1

eternal wing
#

Good

#

Try to transform your limit into something similar

topaz sinewBOT
#

@toxic stirrup Has your question been resolved?

toxic stirrup
eternal wing
#

You want sin(something)/something

#

Just keep the value of the expression the same, but move it and manipulate it in such a way, so that you have sin(?)/?

#

If whatever is inside the sin and in the denominator approaches 0, the limit of that part will be 1

topaz sinewBOT
#

@toxic stirrup Has your question been resolved?

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violet current
#

Can some please help me in this? Is it correct? If not please tell me what is the correct answer and explain it please

violet current
#

<@&286206848099549185>

topaz sinewBOT
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fluid belfry
#

dude like atleast give them some time to even read your question

topaz sinewBOT
#

@violet current Has your question been resolved?

violet current
#

Sorry

violet current
#

Which represents

spark grove
#

f'' on the second picture is the blue one

#

whenever a graph is decreasing, the derivative is negative

violet current
spark grove
#

sorry my english isnt perfect

violet current
#

Like when the graph is being more straight does that mean it going through more the derivatives?

#

f’ straight, and f” more straight

violet current
#

So am I right and got the idea?

spark grove
#

i look at these problems by trying find f(x) first. The (simple) definition of a derivative is a rate of change, so when a function is increaing, that means its rate of change is positive, which means the derivative becomes positive there. If you look at the first picture, the blue curve begins increasing at x=-1. you can notice that the black curve becomes positive at x=-1, so therefore, the black curve is the derivative of the blue curve. notice how when the black curve begins decreasing at x=1.5, the red curve becomes negative, so therefore, on the first picture, the red curve is the derivative of the black curve.

spark grove
spark grove
# violet current f’ straight, and f” more straight

this is a way to think about it, but its not necessarily correct. I think that you are thinking that the derivative function of a polynomial is one degree lower (for example, the derivative of x^2 is 2x) which does make it look straighter in most cases. I wouldn't use that for this type of question though, because you only get to see the graph of the functions, not the equations of the functions itself

violet current
#

Hmmmmm, that was an excellent explanation tbh. I got the idea mate

#

Tysm for helping

#

🤝

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rare jewel
#

Confused about this, only question I really dont know lol

topaz sinewBOT
#

@rare jewel Has your question been resolved?

rare jewel
#

any help

#

: (

topaz sinewBOT
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@rare jewel Has your question been resolved?

verbal crater
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graceful leaf
topaz sinewBOT
graceful leaf
#

hello

#

when i type the -3.5 for X in my calculator is error sadly

#

is this undefined or something like that

verbal crater
#

how did you type it

graceful leaf
#

i take pic 1 sec

#

idk i did the same format for the other ones i guess this one is different

verbal crater
#

huh weird

whole sleet
#

Return ur calculator

verbal crater
graceful leaf
#

oh

#

have to write in those paranthese ok

obtuse tundra
#

No

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U need to use the minus at the bottom

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(-)

graceful leaf
#

oh

#

ok

#

i try 1 sec

whole sleet
#

uh

#

I think your calculator broken man

verbal crater
#

never used one of those calculators lol, always used a casio

graceful leaf
#

I tried that and still error

graceful leaf
#

i just got it tho

#

is this something possible without calculator

#

or its too much

sand ivy
#

@graceful leaf u can simplify first using exponent laws:

(1/5) ^ (-2.5)
= ((1/5) ^ (-1)) ^ (2.5)
= 5^2.5

#

the error probabably has to do with it having trouble doing negative exponents so if u do that by hand u should be able to type it in now

#

or try using negative sign (left of enter) instead of subtraction sign in ur exponent

topaz sinewBOT
#

@graceful leaf Has your question been resolved?

graceful leaf
#

wow thnxs very much

#

let me try ok

#

i forgot to put

#

whole thing

#

tahts why the error

#

Lol

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rigid vortex
#

i'm struggling to understand what the logic from 'inspect these summations further...' and how this changes the indices on the summations so you change the sum to n into a sum to infinity

rigid vortex
#

basically, how does n>=k warrant the step that comes after?

odd pagoda
#

it might help to write out the first few terms of all the sum notations

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south ferry
#

Hello, I have the following logistic regression definition

south ferry
#

it's clear to me, that we can basically treat it as a probability and use it for classification problems.

#

yet I'm confused by $P(Y=y | x;\theta) = \sigma(y\mathbf{x}\cdot\mathbf{\theta})$.

#

resp. confused by how the loss is defined.

#

if we e.g. look up the logistic unit we see

#

so why do we have the y in the argument of our sigmoid?

thorny flameBOT
#

Pascal

south ferry
#

hmm I guess mathematically it kinda makes sense, just somewhat weirdly notated (at least for me) but I still don't understand what's going on exactly.

strange whale
#

re pascal

#

to go back to hyperplanes

#

we're trying to do binary classification here, i.e. we're trying to see where the points x with y=1 are located in space, and same for the x's with y=-1

#

the way we're doing that here is with a hyperplane

#

the hyperplane splits the x-space in 2

#

on one of the half-spaces you'll consider that y=1

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on the other one you'll consider that y=-1

#

that's just basic binary classification

#

now logistic regression tries to add some probability info

#

the closer you are to the hyperplane, the less sure you are about the result (1 or -1)

#

and conversely the farther you are, the more sure you are about the result

#

just trying to give a very high level view of what's going on here

south ferry
#

yeah I get that mostly but I fail to properly interpret the math here.

strange whale
#

you want to say something else or no ?

south ferry
#

We have a bunch of data points with labels and we draw a line that separates them (in a 2D case) i.e. we tune theta. Right? Now how do we tune theta, we do that by defining a loss function and then solveing the resulting optimization problem. In our case, the loss function is the cross entropy i.e.

H(p;q) = - sum_i( p_i* log(q_i)) (iirc)

Now p is basically the "distrbution of our labels" i.e. "y". We only have i=1 so we get -y*log(q_i)

hmm i remember that yesterday, when I looked at that I didn't fully get the connection which is probably why I struggle now.

#

I guess I'd rather bother a TA with that.

#

I really wanna see it being derived properly

strange whale
#

hoping the TAs are willing to

#

I gtg pretty soon also

#

unfortunately

south ferry
#

otherwise math stackoverflow 😛

strange whale
#

I'll force them to, whatever the cost

strange whale
#

just wondering, what's that book you got ?

south ferry
#

ah just lecture notes from a deep learning course

strange whale
#

ah okey

south ferry
#

it's not public but I think the course is based on

strange whale
#

alright alright

south ferry
#

maybe

#

Logistic regression is basically just taking a linear assumption e.g. f(x) = x * theta and then defining a loss function lik e.g.

  • Perceptron
  • least squares
  • log loss

and then optimizing theta, right?

strange whale
#

well ultimately yes that's the goal

south ferry
#

funny how I probably did all that stuff a shit ton of times but never really tried to understnad the math behind if properly.

strange whale
#

to seperate the -1 and +1 classes in the nicest way

#

nicest being defined by the loss here

south ferry
#

yes

#

thanks you too

#

anyway I have to leave. thanks again.

#

have a nice day you two

#

.close

topaz sinewBOT
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wintry oar
#

Just a quick log question. Log10(3)=m, log10(5)=n Q:find log15(30) in m and n

topaz sinewBOT
#

@wintry oar Has your question been resolved?

wintry oar
#

<@&286206848099549185>

twin linden
#

hi

wintry oar
#

Hi

twin linden
wintry oar
#

Meter?

#

I think it can be rewritten as log10(30)\log10(15)

wintry oar
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.close

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drifting stream
#

How do i solve (-2/cot^2(3t)), i need to derivate.

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#

@drifting stream Has your question been resolved?

steel violet
#

u need derivative of that right

drifting stream
#

Yed

#

Yes*

steel violet
#

first write 1/cot^2(3t) as tann^23t

#

then use chain rule

drifting stream
#

-2 tan^2(3t)?

steel violet
#

yes now use chain rule

drifting stream
#

I dont remember how to do that

#

I derivate 3t?

steel violet
#

in chain rule we follow the rule power function angle

#

first we do derivative of power of tan^2(3t)

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so it will be 2tan(3t) right

drifting stream
#

Oh yes yes

steel violet
#

then we do deriivative of function that is tan3t as sec^2(3t)

#

then we do derivative of 3t

drifting stream
#

-2*2 sec^2(3t)?

drifting stream
steel violet
#

no each step has to be multiplied

#

it will be -2* 2tan3t* sec^2(3t)*3

drifting stream
#

Thats the final answer?

steel violet
#

yes

drifting stream
#

Oh so u dont delete tan

#

U just add sec

#

But where did that las *3 came from?

steel violet
#

derivative of 3t

drifting stream
#

Ohhhh

#

Tytyty

#

Helped me a lot ❤️

#

.close

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fluid belfry
topaz sinewBOT
fluid belfry
#

how did they get h= sqrt 3 L/2

drifting swift
#

either trig or pythagoras

#

you can split the equilateral triangle in half with an altitude

#

it'll have hypotenuse L and legs L/2 and h

fluid belfry
#

yeaa im getting it by pythagoras then

#

Thankyou

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.close

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late crypt
#

Why is arg(z^25)=arg z=(i-1)

topaz sinewBOT
rigid ivy
late crypt
#

X+yi