#competition-math

1 messages · Page 6 of 1

ripe iron
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Thanks guys now I  got it

ornate blade
radiant jasper
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hi everyone

modern prawn
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wrong server

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💀

winter sable
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What

vital glen
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yo

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anybody preparing for imo?

high goblet
vital glen
high goblet
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i almost made it to the team for the internationals but i didn't quite make it

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anyway i'm at uni now so i can't do the IMO anymore

high goblet
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wait r u talking about that one random indian thing called the IMO even though it is not international nor an olympiad?

vital glen
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haven't started studying for it yet

vital glen
high goblet
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send me what ur taking about cus the actual international maths olympiad happened a few months ago in the UK already

high goblet
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the next one is in australia and won't be held until next summer

vital glen
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Yes, that's correct! The International Mathematical Olympiad (IMO) is held annually, but the dates can vary from country to country. In the UK, the selection rounds and national competitions leading up to the IMO are often completed before the international event takes place, allowing the selected team to prepare for the IMO.

In India, the selection process typically involves multiple rounds, including regional and national competitions. The INMO (Indian National Mathematical Olympiad) is usually held a bit later in the year, which means that students in India may still be in the process of preparing for their selection to the IMO team when the event has already occurred in other countries.

vital glen
high goblet
vital glen
vital glen
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got any tips?

high goblet
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ngl i'm still slightly confused by what ur asking abt

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are u saying ur preparing for the regional olympiads in u area?

high goblet
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there's a discord server called maths olympiad discord server which is better suited for maths olympiad questions

vital glen
radiant jasper
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problems like these:

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but easier

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try looking for math olympiad problems more your style

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like AMC or something easier like comps from big companies that steal your money

vital glen
radiant jasper
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just do other problems since they have a whole library of past olympiads

vital glen
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man thank you very muchh!

vital glen
radiant jasper
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i only practice online

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if i were to recommend a book for you maybe some basic fundamentals in olympiad math

radiant jasper
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most problems are asking you to give proof

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ok bye

vital glen
winter sable
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Hi guys

winter sable
vital glen
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yess

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i was talking about the regional level

winter sable
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Yea me

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India

modern prawn
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how smart are you

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wth

high goblet
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but it's really not that hard in the modern olympiad landscape

modern prawn
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dude if thats not a legendary problem then i’m a kindergartener

high goblet
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sorry i didn't mean legendary sarcastically lol

high goblet
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that was a very novel idea that no one had done before

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but then basically "oh look that's a cool olympiad trick" and now suddenly you have a billion questions that all use vieta jumping

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it's not hard in the modern landscape cus basically ppl overused the idea

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to the point where it's more "oh look another vieta jumping question" rather than "damn how do u do this"

modern prawn
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I only know vieta’s formula or whatever and i know that probably is not related at all to “vieta jumping”

high goblet
# modern prawn BRUH

questions like IMO 2007 Q3, IMO2007 Q6, IMO 2020 Q6 are considered the hardest IMO qs in recent history

high goblet
modern prawn
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do u compete in imo

high goblet
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the rough tldr is that this question was really hard but only had 1 trick

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then ppl came up with a load of other questions that all use the same trick

modern prawn
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So its hella easy if you know the trick but impossible if you dont

high goblet
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but if u have a bunch of questions that have the same trick, it eventually becomes 'learn the trick' rather than 'come up with the trick'

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hope that explanation makes sense

high goblet
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the main thing is ppl overused it so it got really boring

modern prawn
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I feel dumber every day I am in this server

high goblet
modern prawn
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I should leave so my ego regains

high goblet
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didn't quite make the IMO team for my country but i got to the final stage

modern prawn
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dude how are u so smart wwttthhh

high goblet
high goblet
high goblet
modern prawn
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are u in college yet

high goblet
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given that u recognised the problem source

modern prawn
high goblet
modern prawn
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back to get my ego destroyed more, what is 1 + 1

normal granite
normal granite
winter sable
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We are skibidi indians

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Maths lives in us🤣

high niche
dry forum
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How do I get faster with calculation?

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Should I focus on techniques, training, or working memory?

radiant jasper
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any hints plzz

radiant jasper
ornate blade
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,w sum n/(n^2 + 2kn + k^2) from k = 1 to n

ornate blade
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what to compare to hmmm

radiant jasper
ocean narwhal
ornate blade
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oh RIGHT

ocean narwhal
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Ye so its just integral of 1/(t²+t+1) from 0 to 1

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,w integrate 1/(t²+t+1) from 0 to 1

gilded haloBOT
ocean narwhal
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So that

ornate blade
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wait

ocean narwhal
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The answer is b,c 💀

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Its a jee pyq

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I dont know why

ornate blade
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yeah it has to do with the summation bounds

ocean narwhal
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But well n is not approaching infinity so i got no clue

ornate blade
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1/(x^2 + x + 1) is a decreasing function in [0, 1] so the left Riemann sum will be larger than the integral
but the right Riemann sum will be smaller than the integral

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the left Riemann sum is T_n and the right Riemann sum is S_n

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that makes perfect sense now that I know the answer lol

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also yeah we are not taking the limit, so the sum will be a finite number of rectangles

ocean narwhal
ornate blade
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left Riemann sum

ocean narwhal
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The Tn is not a proper riemann sum tho i think?

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Everywhere it says n

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It should be n-1

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I think

ornate blade
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nah, the variable in both summations is the k, so it's fine

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basically you know Tn is the left Riemann sum cause it's from k = 0 to k = n - 1
the right Riemann sum would range from k = 1 to k = n

both have n rectangles

ocean narwhal
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I

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Didnt notice the lower bound

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Fuck

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Sorry

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Nvm

ornate blade
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okok

radiant jasper
solid cloud
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Helppp plss

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I don't quite understand how I could turn gcd or lcm into a variable in this

ornate blade
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you probably need the fact that ab - a - b + 1 = (a - 1)(b - 1)

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so add 1 to both sides

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I'm not sure how to proceed

high goblet
high goblet
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like only ~10ppl take it, it's not really a stage of our national olympiads

solid cloud
high goblet
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it's quite a common trick to rewrite our variables a,b

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in terms of a/gcd(a,b), b/gcd(a,b) cus then they're coprime

high goblet
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then write a = dx, b = dy

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then we know gcd(a,b) = d and lcm(a,b) = dxy

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etc.

solid cloud
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Oh shi that is rightt

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Let me do it now

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Tyy

high goblet
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nw!

solid cloud
# high goblet nw!

I'm sorry for asking again, for my question I change all of a into dx and b into dy

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So I write it again as

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D^2xy -dx-dy = d+dxy

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After that I make

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D^2xy = d(x+1)(y+1)

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Then I cross the d

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Dxy=(x+1)(y+1)

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Then I got stucked

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Did I do something wrong here

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@high goblet tyy

high goblet
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but my thought process was to write it as

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d = (x+1)(y+1)/xy

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i.e. (x+1)(y+1)/xy is an integer

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this is a useful condition - why?

solid cloud
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I'm lost bro

high goblet
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if x=100 and y=100

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then (x+1)(y+1)/xy is just very slightly larger than 1

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and definitely smaller than 2

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and certainly not an integer

high goblet
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so let's wlog x <= y

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can u find a restriction on x?

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if x>=3, what can u say about (x+1)(y+1)/xy

solid cloud
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I'm truly lost here

high goblet
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so if x>=3, y>=3 which means

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$(\frac{x+1}{x})(\frac{y+1}{y}) \leq \frac{16}{9} < 2$

gilded haloBOT
high goblet
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can u use this to finish off the problem?

solid cloud
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Alr let me tryy

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By the way @high goblet why did you use x>= 3 and y>=3 why Did you use 3 in here

high goblet
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(maybe if x>=3 then we can force it to be less than 2)

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(oh it works)

solid cloud
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Huh how??

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This is new math knowledge I must learn bro

high goblet
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as in this is quite a common trick that appears in quite a few questions

high goblet
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but isn't likely to be an integer for very many values of x,y

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because you can bound it between i.e. 1 and 2 for a lot of values of x,y

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then wlog x <= y

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and take a guess for x (i.e. x>=3)

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then if that inequality works, you know x=1 or x=2

high goblet
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try x>=4 etc.

solid cloud
high goblet
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we have x=1 or x=2 now

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try to finish from there

solid cloud
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Alr

high goblet
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and this q

solid cloud
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@high goblet is there a name for this trick so I can learn it

high goblet
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bounding?

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finding inequalities to bound a quantity is very common and comes up like everywhere

solid cloud
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Dividing both by 2

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(Y+1)y <= 8/9

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Not possible for positive integer

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Is this explanation right??

high goblet
solid cloud
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💀

high goblet
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so we've said that (x+1)(y+1)/xy is an integer

solid cloud
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Alr ty let me try to do it

high goblet
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so we need to test x=2 and x=1

solid cloud
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What should I done

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This material is beyond my level rn

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I join some math competition but never see this material come out

high goblet
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i think it might be helpful to try to understand the solution

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Write $a=dx, b=dy$ where $d=gcd(a,b)$. Then our equation becomes:
$$d^2xy - dx - dy = dxy + d$$
i.e.
$$d = (1+\frac{1}{x})(1+\frac{1}{y}) \in \mathbb{N}$$
Clearly $(1+\frac{1}{x})(1+\frac{1}{y}) > 1$. Now wlog $x\leq y$. Then if $3 \leq x \leq y$ then
$$(1+\frac{1}{x})(1+\frac{1}{y}) \leq (1 + \frac{1}{3})(1 + \frac{1}{3}) = \frac{16}{9} < 2$$
and so is clearly not an integer. Thus, $x=2$ or $x=1$. \
If $x=2$ then $\frac{3}{2}(1+\frac{1}{y}) \in \mathbb{N}$. If $y > 3$ then we get another contradiction and thus $y=3$, giving us $d=2, x=2, y=3$ as a possible solution. \
If $x=1$ and $y \geq 3$ then
$$2 < 2(1+\frac{1}{y}) \leq \frac{8}{3} < 3$$
and so not an integer. Thus, $y=1$ or $y=2$. It is trivial to see that these work and thus $x=1, y=1, d=4$ and $x=1, y=2, d=3$ are 2 further possible solutions. \
Hence, the solutions to our original quesiton are $(a,b) = (4, 6), (6, 4), (4, 4), (3, 6), (6,3)$

gilded haloBOT
solid cloud
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Thank you

high goblet
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nw

solid cloud
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Bruhhhh

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That is whyy

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I understand

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I make the x a internet but I didn't make sure the original "a" variable also an interger

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Oooh I forgot

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Can anyone explain me how should I try to approach the number 2 question about 100 digit real number

high goblet
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fix the sum of the digits then try to find a number that satisfies the properties you want

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remember that we don't really have any good ways to test if i.e. n is divisible by 19 etc.

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so u want to make the sum of the digits nice

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think about how u can do that

solid cloud
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Alr

solid cloud
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I make number where the sum of the digits will be 125

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1......125

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I though it would work

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@high goblet

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Where there is 96 spot left for the rest of the number

solid cloud
high goblet
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u just have to fudge ur numbers a bit

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so that the sum of the digits is 125

solid cloud
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Yeah

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There is many variation using 1 and 2

solid cloud
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How should I factor a+b=a^2-ab+b^2

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And how should I prove number 9

gusty verge
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Sum of squares is usually destroyed by Cauchy Schwarz

novel forge
gusty verge
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Cauchy Schwarz:

[\left(\sum_{i=1} u_i v_i\right)^2\le \sum_{i=1}u_i^2\sum_{i=1}v_i^2]

Then take $v_i=1$ and $u_i$ as in the sum they showed, then rearrange.

gilded haloBOT
solid cloud
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Alr let me try it

cunning bloom
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Hello guys
I need references for which book I can use for Maths for class 12th boards?

tribal notch
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How do I actually learn from my mistakes? I understand how to solve that particular problem now, but couldn’t apply the exact same thing in a different context

modern prawn
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wat

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can you elaborate further

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your description is kind of weird

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sorry, just cant understand

solid cloud
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Sorry I'm kinda lost here

jolly solstice
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I'd multiply both sides by (a+b) since that seems potentially interesting

warped wedge
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has anyone here done the official aops amc12 mocks

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how does it compare with actual amc12 in terms of difficulty

jolly solstice
# solid cloud Sorry I'm kinda lost here

well I guess we know it's some conic section, and it's symmetrical across the line a=b. Solving gets us 2 points, so that means it's either an ellipse (good finitely many things to check) or a hyperbola (boo infinitely many things to check). We know it's not a hyperbola because... well I just checked the points at infinity in the projective plane but probably less fancy way to do this by trying to find asymptotes or something.

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of course this is all ad hoc rationalization, I just graphed it in desmos lol

solid cloud
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Then I used quadratic formula

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Then just found x and y

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X = a, b=y

jolly solstice
solid cloud
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There

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So there is 6 pair

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How should I try to approach this question

radiant jasper
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can some solve htese tqo

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two

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jsut give me hints

ivory ember
gilded haloBOT
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Civil Service Pigeon

ivory ember
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  1. Direct Cauchy Schwarz question
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(Question 1 isn’t well posed imo tho)

radiant jasper
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can some one just solve thje first question

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q1

solid cloud
ivory ember
scarlet rootBOT
radiant jasper
gusty verge
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(once you apply CS and remembering you can choose the different letters arbitrarily, you can essentially show the minimum of the expression is 0, which is too low)

high goblet
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often in inequalities, you have something that looks nice, but often the first step to solving it is just to expand out

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anyway u end up with this

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this looks horrific

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partially because we have ws multiplied with xs and ys but not zs etc. etc.

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can u rewrite this in a nicer way?

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then u can apply C-S and finish

solid cloud
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Ly saving me once again

solid cloud
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Like give me a hint how to use Cauchy schwarz in here

high goblet
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notice that w^2 is multiplied by x^2 and y^2

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and z^2 is multiplied by x^2 and y^2

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anyway stare at it and realise that we have

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(w^2 + z^2)(x^2 + y^2) + 2wx + 2yz + 2 >= 1

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now u can CS that

tall quartz
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Find all natural numbers (a,b) such that ab| a^2024 + b. Can anyone help me with this??

high goblet
high goblet
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a | a^2024 + b

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so a | b

shadow dirge
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Maybe thats the ans

high goblet
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then if a | b write b=ab'

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then a^2 | a^2024 + ab'

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so a | b'

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repeat that basically until u get a conclusion

shadow dirge
high goblet
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a | ab and ab | a^2024 + b so by transitivity

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a | a^2024 + b => a | b

shadow dirge
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Oh i see

wheat kettle
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does anyone have any tips on studying for short-answer contests? aka for getting faster and doing less mistakes

dusk tendon
wheat kettle
dusk tendon
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ohh

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i cant help you i have no experience w that

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sorry

wheat kettle
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its ok

dusk tendon
# solid cloud Sorry I'm kinda lost here

i completed the square on the RHS, then multiplied everything by negative 1 to get ab-a-b=-(a-b)^2, then i added 1 to factor the LHS by sfft (simons favorite factoring trick). when we factor, we get (a-1)(b-1)=1-(a-b)^2. we factor RHS by difference of squares for (a-1)(b-1)=(1-a+b)(1+b-a). now we see that 1-a+b=a-1 and 1+b-a = b-1. solving the system of equations gives a = -2 and b = -2 which are the only ones i think (i could be wrong)

elfin crown
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idrk if I should be asking this here, but is this channel used for discussion about how to solve comp questions (ie, the last 5 questions of AMCs) or just kinda talking about the comps in general

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I joined like, five minutes ago so I know nothing 😭

elfin crown
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alrightyy

dusk tendon
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starting with amcs is easy

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just make an aops account and do the mocks and use their books

elfin crown
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I took an aops class and I lowkey hated it

dusk tendon
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dang which one

elfin crown
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i dont really remember, apart from the fact that it was on the amc10 and discussion strategies

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I also did the seminar

dusk tendon
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oh amc 10 problem series probably

elfin crown
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yeah probably that

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I prefer face to face teaching, which was probably why it was so tedious

dusk tendon
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yeah

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i havent done any classes yet but if you just use the books from aops (intro series and volume 1) and do questions it will boost your score

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and also do mocks

elfin crown
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are the books free??

dusk tendon
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no

high goblet
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that doesn't follow from (a-1)(b-1)=(1-a+b)(1+b-a)

high goblet
dusk tendon
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idk i may be wrong

high goblet
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but yeah generally multiple choice qs don't really matter

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idk how it works in the US system

wheat kettle
high goblet
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ah k

wheat kettle
high goblet
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what r the questions like?

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i think in general, just do qs

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multiple choice qs are usually followed by like the harder more prestigious competitions anyway

wheat kettle
high goblet
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probably do them timed

wheat kettle
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I thought if I just got really smart I would automatically think these contests are easy but they are not

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I mean, each question is easy

wheat kettle
dusk tendon
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can you give an example of a question

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just want to see the difficulty

wheat kettle
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hum I'll find one with pretty median difficult of each contest

dusk tendon
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ok

wheat kettle
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how many ways can we color each labeled point with red, blue and green such that no 3 colinear points have the same color

high goblet
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yeah probably just do questions to eventually build up speed

wheat kettle
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well from obmep every question is straight up extremely easy so it's REALLY just not getting anything too wrong or thinking too much

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I'll send one that I could not solve fast because my brain hurt a little

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Benício put together, twice, three dice in such a way that faces in contact have the same number, each time he summed the numbers in all faces that are not in contact and the difference between the sums was 16. which were the numbers in the faces that were never in contact?

wheat kettle
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maybe I'll do like a daily amount of questions or something as the actual shore it is

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maybe weekly for flexibility idk

high goblet
radiant jasper
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can you translate to english

wheat kettle
radiant jasper
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oh

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mb

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ew counting

wheat kettle
high goblet
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ic ic

wheat kettle
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+the standard is each school forcing all students to take it but my school doesn't do that so only 2 people per level can pass to the second phase which made me unable to do it this year

wheat kettle
warped wedge
#

`has anyone here done the official aops amc12 mocks
how does it compare with actual amc12 in terms of difficulty

radiant jasper
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they are very orz

ripe iron
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x²+4y²+9z²-2x-12y+6z+10=0
Show that 1/3≤x+y+z≤4

ripe iron
# ripe iron x²+4y²+9z²-2x-12y+6z+10=0 Show that 1/3≤x+y+z≤4

x²+4y²+9z²-2x-12y+6z+10=0
⇔x²-2x+1+(2y)²-12y+9+9z²+6z=0
⇔(x-1)²+(2y-3)²+9z²+6z=0
⇔(x-1)²+(2y-3)²+9z²+6z+1-1=0
⇔(x-1)²+(2y-3)²+(3z+1)²=1
0≤(x-1)²≤1
⇔0≤|x-1|≤1
⇔|x-1|≤1
⇔-1≤x-1≤1 |+1
⇔0≤x≤2
⇔x∈[0;2]

0≤(2y-3)²≤1

⇔0≤|2y-3|≤1
⇔|2y-3|≤1
⇔-1≤2y-3≤1 |+3
⇔2≤2y≤4 |:2
⇔1≤y≤2
⇔y∈[1;2]

0≤(3z+1)²≤1

⇔0≤|3z+1|≤1
⇔|3z+1|≤1
⇔-1≤3z+1≤1 |-1
⇔-2≤3z≤0 |:3
⇔-2/3≤z≤0
⇔z∈[-2/3;0]

min (x+y+z)
=min x+min y+min z
=0+1-2/3
=1/3

max (x+y+z)
=max x+max y+ max z
=2+2+0
=4

⇒ 1/3≤x+y+z≤4

gusty verge
#

Nice

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But you can use latex on discord

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A lot easier than having to copy $\in$ and $^2$

gilded haloBOT
royal estuary
#

$$ 2^p \neq 3m + 1 $$ prove for positive odd integer values of p and m

gilded haloBOT
#

Mr.Bombastic

royal estuary
#

Need help

ornate blade
# ripe iron

without loss of generality, note that the inequality is homogenous, as in $(a,b,c) \mapsto (ka,kb,kc)$ for $k \in \mathbb R \setminus {0}$ doesn't change the inequality

gilded haloBOT
#

higher's secret twin brother

ornate blade
#

so we can let $abc = 1$

gilded haloBOT
#

higher's secret twin brother

ornate blade
#

AMGM gives $\ge 3 \left( \left| \frac{abc}{(b + c)(a + c)(a + b)} \right| \right)^{1/3}$

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hmmmm

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oh if you can show that (a+b)(b+c)(c+a) >= 8abc you're done

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wait that's the wrong direction sorry

gilded haloBOT
#

higher's secret twin brother

ocean narwhal
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but this part is easy

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just apply am gm in a, b then in b,c then in a,c

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and multiply

ornate blade
ornate blade
ocean narwhal
#

lemme think

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nvm i give up 💀 how would you even

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that looks an awful lot like it need the GM-HM

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but then there's inequality sign

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nd HM is smallest of them all

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you cant really compare

ornate blade
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oh the inequality isn't sharp

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if in doubt just Approach0

ocean narwhal
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thats cheating

ornate blade
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no it's not

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if you've made an honest attempt

ocean narwhal
#

true that

ornate blade
#

also comp maths people rarely give detailed solutions

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you always have to fill in the gaps yourself

sand hull
south birch
#

I agree

ripe iron
untold thunder
jolly solstice
#

I suppose (1+sqrt(5))(1-sqrt(5))=-4 is not a coincidence that 4 is in the denominator, idk

untold thunder
#

It is 🥶

jolly solstice
#

you have the answer?

untold thunder
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Yes I have a full solution

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It's very long so there may be some error but I think I have the general idea

jolly solstice
#

gotcha, yeah I guess there may be more than one way to do it, but if you didn't use that fact that's good to know

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oh I think I see a way to do it

#

,texsp ||think we can replace the $a_k$ and $b_k$ with these then work out the geometric series we get, assuming they converge $$\sum_{k=1}^\infty \frac{\frac{(1+\sqrt{5})^k+(1-\sqrt{5})^k}{2} + (1+\sqrt{5})^k-(1-\sqrt{5})^k}{4^k}$$||

#

no idea if that actually spoilers the texit, I know there is/was a way for texit to spoiler and I have spoilers to auto-show

cerulean ibex
#

,texsp

gilded haloBOT
#

Please give me something to compile, for example latex ,tex The solutions to \(x^2 = 1\) are \(x = \pm 1\).See ,help and ,help tex for detailed usage and further examples!

cerulean ibex
#

this is not spoilered

gilded haloBOT
#

Merosity

jolly solstice
#

that do it?

cerulean ibex
#

yep!

jolly solstice
#

ty ty

cerulean ibex
#

nw i just learned abt it a couple days ago

untold thunder
jolly solstice
#

it's really just 2 geometric series

untold thunder
#

Oh wait

cerulean ibex
jolly solstice
#

you can kinda work it through with +- on the sqrt too to get both in one go if you're really wanting to be cute

untold thunder
#

Yeah I think that works, but the idea that I thought was cool with that problem is you can actually find a closed form for a_i and b_i (Kinda)

#

If you want to try and solve it that way you can

#

By all means it's harder though

jolly solstice
#

interesting, would be curious to know

#

well do we get the same answer I just worked it out and got -2/sqrt(5)

#

I wouldn't be surprised if I made a mistake though lol

untold thunder
#

I checked my longer solution through demos and stuff (because you can) and honestly, it would probably never have a radical form like that in the end I probably made a mistake too

cerulean ibex
jolly solstice
cerulean ibex
#

maybe the sums end up nice catthink

#

i dont see any other way to elementarily get a closed form

jolly solstice
#

that was the first thing I did tbh but didn't see anything

#

then just noticed I could write a_k, b_k in terms of the exponentials so it'd all thread through the geometric series

#

so that's where I gave up, maybe some combinatorics trickery can be done though on those binomial coefficients

#

maybe we want to expand 5=(1+4) and do another binomial expansion there, cause, idk 4

#

swap the sums

cerulean ibex
#

i'm not sure i believe in a 'true' closed form

#

i think you can show some things

untold thunder
#

Like not completely but better than a bunch of terms

cerulean ibex
#

i think they both have to be divisible by some power of 2

untold thunder
#

I have a hint to start

jolly solstice
#

I feel like I've already finished lol

untold thunder
#

You don't have to explain your process what was your "closed" form for a_i and b_i?

#

It should have Fibonacci numbers in there

jolly solstice
#

I could see that

jolly solstice
#

you can see it from the binomial theorem when you combine them, the sqrt(5) and -sqrt(5) terms will either cancel or double

#

$$a_k = \frac{(1+\sqrt{5})^k+(1-\sqrt{5})^k}{2}$$

gilded haloBOT
#

Merosity

untold thunder
#

basically my "answer" is just the exponential of the radicals replaced by Fibonacci numbers because they're easier to work with

jolly solstice
#

this is a general trick, for instance you might have seen people do this to get the real part of an imaginary number

#

here they're replacing sqrt(5) with sqrt(-1), but you're still adding/subtracting conjugates

untold thunder
#

yeah I've seen that

jolly solstice
#

actually my b_k should have a sqrt(5) in the denominator

#

to divide that out

#

so my answer in the end was wrong, but I'm not gonna go through and fix it

untold thunder
#

This is what I got in terms of Fibonacci I did this really weird method that might not be necessary though $a_n=2^{n-1}(F_n+F_{n-2})$, $b_n=2^{n-1}F_{n-1}$

#

wait I think tyop

gilded haloBOT
jolly solstice
#

I see what you mean about fibonacci I've seen something similar before so I can see that working out that's a cool idea

#

ok worked out some recurrence relations, by taking the kth term and multiplying by (1+sqrt5) to get the k+1 term and collectin gcoefficients, but doesn' tquite line up how I was expecting. But reading your message a bit closer now I'll see if that works
$$a_{k+1}=a_k+5b_k$$
$$b_{k+1}=a_k+b_k$$

gilded haloBOT
#

Merosity

jolly solstice
#

or rather, I can just diagonalize the matrix now to get the answer

untold thunder
#

I used vietas formulas to get that

jolly solstice
#

oh?

#

I collected terms the were on sqrt5 or not on this, if that's what you mean $$(a_k +b_k\sqrt{5})(1+\sqrt{5})=a_{k+1}+b_{k+1}\sqrt{5}$$

gilded haloBOT
#

Merosity

untold thunder
#

You can find the quadratic with the root (1+sqrt5)/2 and then do some induction to find a_k and b_k

untold thunder
ebon sigil
#

Who else doin math counts

soft vigil
#

good memories

modern prawn
#

in mathcounts do you compete infront of a lot of people or is it just a boring classroom environment

#

like if ur just doing a local school mathcounts

elfin crown
#

You do it in a school environment

soft vigil
#

224 kids

#

4 kids per table who are on the same team

#

Environment is great

shadow spruce
#

😭

lyric parrot
#

solve in 2 mins

#

hint: find tan (a+b)/2

ornate blade
#

smh

lyric parrot
#

its a really good question for olympiads so i wanted to share it

ornate blade
#

probably square both equations and add them to get $2 + 2 \cos(\alpha - \beta) = \frac{6}{9} + \frac{3}{9} = 1 \implies \cos(\alpha - \beta) = -\frac{1}{2}$

gilded haloBOT
#

higher's secret twin brother

serene pewter
ocean narwhal
ornate blade
#

idk

rose mortar
#

Anyone good at complex numbers dm me I have a problem

#

Thx

fast coral
rose mortar
fast coral
#

dont dm me bruh ask it here

rose mortar
#

Uhhh ok

#

So my teacher had shown me a method to generate Pythagorean triplets using 2 other triplets
Using complex numbers

#

So I thought that I should generalise it

#

And I have an equation
It would be brilliant if someone could check it

slim oriole
rose mortar
lyric parrot
# slim oriole will you provide the solution?

Alright so
Find [2sin(a+b)/ 2]cos (a-b)/2 which is basically sin a+ sin b( its a basic identity you can look up the proof on yt)
And similarly [2cos (a-b)/2]cos (a+b)/2 = cos a+ cos b (eq1)
Divide both the equations then u get tan (a+b)/2
Then just apply tan^2(x)+1=sec^2(x)
With this you find cos (a+b)/2
Substitute in eq1 to find cos (a-b)/2
Simply square it and multiply by 100, boom you solved it

#

The question is find 100cos^2([a-b]/2)

#

It's a fun question to solve

#

Sure shot olympiad question

slim oriole
#

the request is fucking wrong

modern prawn
#

how are people so smart lol

ornate blade
#

jesus

#

yeah I was scratching my brain and all that time

winter sable
#

hi guys i m back

long wharf
#

im the smartest

ebon sigil
#

lol math counts is light work

#

it's 6-8

#

but it really shouldn't matter

#

cuz math counts should rep the smartest schools

ornate blade
#

I bet you couldn't do the questions as fast as the finalists

#

if you could work on each question for as long as you like then it'd be easy

#

also yeah they are challenging cause they are extensions of middle school material without going to more difficult stuff

novel karma
#

why won't my school let me take both amc 10a and 10b

#

i thought you could

#

am i wrong

ornate blade
novel karma
ornate blade
#

the AMC doesn't care but the AMC isn't the one organising the details of the contest

novel karma
#

huh

ornate blade
#

they'd choose either the A date or the B date

novel karma
#

oh

modern prawn
#

the mathcounts has really easy questions

#

a standard 8th grader doing algebra 2 could easily answer every question they give even in national mathcounts

#

its just you gotta do it fast as hell

fossil loom
modern prawn
#

its true

soft vigil
#

its not true

modern prawn
#

so what level would you AHVE to be as a student to be able to solve these problems without a time limit in your perspective?

soft vigil
#

without a time limit is much different

#

with time limit you need a lot of knowledge on tricks and stuff

modern prawn
#

What is the highest “higher level math” that you’re talking about here

soft vigil
#

i know for sure a standard 8th grader would be scared shitless of this

#

and this isnt even a nats problem

soft vigil
#

to speed up the process a lot

modern prawn
#

I mean i would be scared because i AHVE to do it fast but its like a final end of term exam for geometry kind of question

soft vigil
#

then solve it right now

modern prawn
#

im eating

soft vigil
#

ok

#

go eat instead of typing

modern prawn
#

ok

#

cya

#

ima just watch youtube then

radiant jasper
#

this problem is sus

#

@soft vigil was this a sprint problem

soft vigil
#

p27 of states in 2023-2024 year

radiant jasper
#

wtf

#

ngl i would ksip this

#

perfectly normal quadrilateral

soft vigil
#

just extend AD

#

to intersect CB

radiant jasper
#

yeah

soft vigil
#

wait no

#

its $\sqrt{3}$

gilded haloBOT
#

buboblakistoni

fossil loom
cerulean ibex
#

coordinate bash to find B, three points uniqely define a circle, find the center with said three points, use it to figure out radius, pir^2

#

is the obvious way

#

there's probably a nice trick

fossil loom
#

valid

cerulean ibex
#

not in the spirit of the original quote but yes, coordinate bashing, the devil's marvelous machine

#

i would just use linalg or something here, i'm sure it works

#

but that's the obvious soltuon

fossil loom
#

not even sure I can solve it, granted I don't do comp math, but I'm still a grade 11 honors math student, no way in hell an average 8th grader who hasn't taken geometry is getting that

fossil loom
#

i have now filled a page with diagrams and am not anywhere nearer solving it

cerulean ibex
#

do u know how to get to the center from the three points

fossil loom
#

i can do it with a lot of trig, but mathcounts is no calculator right

compact lion
#

hi please someone can tell me how to prepare for olympiad geometry from basic/intermediate to olympiad level/

idle fjord
#

Any math helpers dm me

cerulean ibex
fossil loom
cerulean ibex
#

mm ig but can't you just solve for the center directly

#

like

#

take the three points you have

#

then consider the equation for a circle

#

plug them in to get three equations

#

with a little bit of manipulation this is a linear system so you can just solve for the center

#

then boom

high goblet
#

that's also probably why i almost made the team

high goblet
#

anyway what sort of olympiad level r u talking about? USAMO?

high goblet
compact lion
high goblet
#

oh as in r trying to improve ur geometry skills to be good enough at IMO geo?

#

or like trying to get to IMO?

#

anyway i can offer some basic advice though:

high goblet
#

ah k

winter sable
#

hi guysy i m back i hope you all recognise me

#

i am sig,a

#

m

reef condor
#

Oinks

south socket
#

Visiting the farm where several dwarves live, Bob organizes 4 forest trips, each of which is attended by all the dwarves on the farm. Each gnome has a red, a white and a black cone. The dwarves use one of their cones on each trip. After examining the colors of the cones used by the dwarves on the trips, Bob notices that no two dwarves use the same color cone on more than one trip. According to this, what is the maximum total number of dwarfs on the farm?

radiant jasper
reef condor
#

ook

radiant jasper
#

skibidi

radiant jasper
idle fjord
#

any math helpers?

south socket
#

what is your solution

pallid ginkgo
#

what does 3-6 and 2-4 mean? is there like a consistent way of ranking olympiad difficulties?

pallid ginkgo
#

whats the diffrence between competition and olympiads

ornate blade
pallid ginkgo
#

why is the intermediate competition split from the others and why is it not called intermediate olympiads?

ornate blade
#

yeah so basically they mean competitions are anything not at Olympiad level

#

i.e, in the IMO sequence

#

olympiads test the foundations of IMO level material or are IMO level themselves

high goblet
#

i suspect that's probably the AOPS ranking

#

MODS 1-10 is also sometimes used

#

Evan Chen has also rated like all the olympiad qs in MOHS

high goblet
ornate blade
#

it's complicated by the fact a lot of competitions style themselves as olympiads

pallid dragon
#

specifically this

#

so you can do 9 dwarves i don't know if it's the largest

south socket
#

Thanks

winter sable
#

do you remeber me

#

i was here 5 texts ago

broken halo
#

please do not

cerulean ibex
#

<@&268886789983436800>

#

sounds scammy

brave ocean
#

please don't advertise unsolicited here.

cerulean ibex
#

thanks smay!

solid cloud
#

100a + 64 and 201a+64 is both squared number Less than 10000 what is a

#

I try to make it to

#

A^2-b^2

#

(A-b)(a+b)

#

So I could get 101a = (x-b)(x+b)

#

After that I'm confused

#

Or did I do something wrong

high goblet
high goblet
high goblet
solid cloud
#

How bout I make x-b is equal to a and make x+b equal to 100

solid cloud
high goblet
#

why is the optimal not x-b = 2a or whatever?

brave heron
brave heron
brave heron
loud gull
#

The MIT high school math contest has an algorithm to dynamically decide problem weights based on how many people solved the problem.

loud gull
#

Putnam publishes data for problem score distributions so you can judge the difficulty of a given problem. It also publishes the function of total score vs. rank. The above plot is an averaging of this function over many years. Do other contests publish such data?

grizzled kestrel
#

Hello

#

May i know whats this channel for

high goblet
#

also i realised my thing isn't as straightforward as i assumed it would be

#

u can eliminate the a and end up with a pell's equation

#

pell's equations are quite well-studied so if u end up with that u can just use theory to finish the problem

boreal sky
#

Is $f:[0,\infty) \to [0,\infty)$ such that
[f(x+y)=f(x)+f(y)]
For all $x,y\in [0,\infty)$ only have $f(x)=cx$ as the solution? If so, what's the proof on it?

gilded haloBOT
#

Its_TheMathCraft

brave heron
high goblet
#

what if you can split a=12 say and it's actually split 101*2 and 6

high goblet
#

but you haven't found all a

high goblet
#

you can probably extend ur original f by setting

#

g(x) = -f(-x) for x negative

#

probably can then show g satisfies the F.E.

#

so f is the +ve side of a cauchy FE solution

#

and bcus pathological cauchy FE solutions are dense in R^2, we must have f(x) = cx

high goblet
#

it might not be true

deft wraith
#

Is it worth doing later AIME problems as practice just for mathematical/ problem solving skills? My country uses BMO1/ 2 which are easier than JMO but are proof based. I think my proof writing skills are fine but is it worth doing those problems just for the sake of improving maths for olympiads?

glad zinc
glad zinc
ornate blade
#

oh shit I didn't read, right

deft wraith
ornate blade
#

agreed there's even a huge difference between further and STEP

#

in terms of format and everything

glad zinc
ornate blade
#

like even if STEP isn't about proofs, the standard of working is pretty high

#

they prompt you very little

glad zinc
#

Are you doing this for STEP prep?

ornate blade
#

you're supposed to just write a page of working naturally without needing hints

deft wraith
#

no i'm doing this for bmo1/2 prep

glad zinc
#

If so then you should definitely do most if not all of normal and further a level maths, then do the STEP prep modules

deft wraith
#

step prep is adjacent too as well

#

also trying to understand a level fm concepts a bit more ref:

glad zinc
glad zinc
deft wraith
#

i just started year 13

#

ive finished maths and further maths

glad zinc
#

I see

deft wraith
#

the books are a bit easy

glad zinc
deft wraith
#

ive had a look at all of the official aops ones

glad zinc
#

Weird, did you do the BMO last year?

deft wraith
#

yeah

glad zinc
#

Result/

#

?

ornate blade
deft wraith
#

yes cambridge

deft wraith
#

i got lucky -- last years paper was very easy compared to other years

#

and i wasnt very good last year

glad zinc
#

Quite strange because I found their books quite useful and I also got low distinction on BMO1 and iirc merit on bmo2

deft wraith
#

vol2?

glad zinc
#

vol1 was almost fully easy, just that odd thing here and there, vol2 was decent

deft wraith
#

i'm using mont and art and craft of problem solving by paul zeitz

#

i need to learn how to do functional equations properly

glad zinc
#

I was in y11 when I sat the BMO btw so maybe thats the reason

deft wraith
#

maybe yeah

#

what year are you?

glad zinc
#

Y12 now

#

SMC was so free this year

#

got full marks

ornate blade
#

bro

#

jacked

glad zinc
#

ill get cooked in BMO dont worry i have done 0 prep cause im a lazy mf

deft wraith
#

i got 120 haha i just made a stupid mistake on the dice question

#

but bmo qualification is all that matters

#

anyway for me i just want to get into cambridge over all of that

glad zinc
#

Getting the dice one wrong is just

#

wild

#

Did you not know that the opposite sides add up to 7?

deft wraith
#

i did the algebra and i went to plug in the solutions so i could see straight away 4 would work so i thought thats the answer

#

if i had tried 2 i wouldve realised oh right they sum to 7

glad zinc
#

I guessed the circle area question

deft wraith
#

a lot of my friends got question two wrong so hahaha

glad zinc
#

Time to make new friends

#

I want to sit STEP in y12, I need to do 2.5 chapters a week then go through all the step modules and past papers 😭

deft wraith
#

both step papers?

glad zinc
#

Yeah

deft wraith
#

nice

#

i think just doing questions is the main thing

glad zinc
#

My goal is s,s but its probably not gonna happen

#

not probably

#

like definitely

deft wraith
#

then just sit it in year 13

glad zinc
#

Yeah but I want to increase chances and also want to use it to show other UK and US unis

deft wraith
#

could you help me with my question that i linked?

glad zinc
#

Let me have a look

glad zinc
deft wraith
#

Yeah that's what I mean by I can do the algebra but I don't get how they affect it geometrically

glad zinc
#

Honestly mate, I don't know, my class is starting this content in a couple lessons and my teacher gave me a question so I could get started early and my research from thats all I know

deft wraith
#

yeah no worries

#

what a levels are you doing?

glad zinc
#

This is the question $Let ( z_1 = a + bi ) and ( z_2 = c + di ). Determine the locus of ( z_3 = \frac{z_1}{z_2} ) as ( c ) varies.$

gilded haloBOT
#

Bitwise
Compile Error! Click the errors reaction for more information.
(You may edit your message to recompile.)

glad zinc
#

Oops

ornate blade
glad zinc
high goblet
#

BMO1 -> BMO2/IMO easy -> IMO/ISL

#

do u have the BMO1 book?

#

forgot the name of it

ornate blade
glad zinc
high goblet
#

and then i just started doing problems i enjoyed

high goblet
deft wraith
high goblet
#

(so p2/p5 standard)

deft wraith
#

i've been doing around 4-6 questions a day

high goblet
#

yeah u'd be surprised, IMO easy questions are a lot easier than u mightthink

high goblet
high goblet
#

once ur done with that work through the entire BMO2 book

#

and that should certainly be enough for camps

deft wraith
#

what about theory specific i.e mont

glad zinc
high goblet
deft wraith
#

modern olympiad number theory

#

it's quite good

high goblet
#

oh right

#

with theory i think it's just something u'll pick up over time

deft wraith
#

i'm trying to brush up on number theory for itnerviews too

high goblet
#

as in like u'll do problems

#

often with BMO1 questions u can learn the theory bit by bit

glad zinc
#

@high goblet What was your best placement in BMO2?

high goblet
#

EGMO is a very good book

deft wraith
#

egmo is a bit hard i've been avoiding geo

high goblet
#

(not european girl's maths olympiad lol, euclidean geo book)

deft wraith
#

i've heard no euclid geo in interviews so like

high goblet
#

basically everyone in like trincamp will have a copy

high goblet
deft wraith
#

i can sort of bash around/ just do bmo1 geo anyway without much but for bmo2 i mght use it like post interview

#

to prep for bmo2

high goblet
high goblet
glad zinc
high goblet
#

and then once u've learnt enough u can then often bash the end of the problem

high goblet
#

where r u applying out of interest?

deft wraith
#

trinity, cambridge

#

i heard they give oly style so yeah

glad zinc
#

Why trinity?

ornate blade
#

this chat is so British my water turned into tea

high goblet
#

basically NT is quite oly-specific and spec-specific (i.e. we did 0 NT in our school) so any NT you get in interviews will basically be approachable without having to know i.e. FLT etc.

high goblet
high goblet
deft wraith
#

i was going to ask where to find mechanics questions of suitable difficulty?

high goblet
ornate blade
# high goblet ahaha

Armand from KoreanEnglishman goes to Cambridge
apparently this other guy from Cambridge saw him around campus a few times

deft wraith
ornate blade
#

sorry for derailing chat

high goblet
#

on my test, there were 9 non-mech questions and 1 mechanics question

#

looked at the mechanics question and went 'nope'

ornate blade
high goblet
#

so i did all 9 other qs

ornate blade
#

right

high goblet
high goblet
ornate blade
#

also Cambridge is insane for not allowing resits
I heard some really bad things about students who have a medical emergency and the administration has no mercy

deft wraith
#

easy ones

deft wraith
#

i've done the sample ones

#

it's only like 1 or 2

high goblet
#

we're not meant to share our interview questions lol

deft wraith
#

there's this really weird sample question as well let me show you

deft wraith
high goblet
#

but i can DM u like my rough memory of my interview questions if u want them

high goblet
deft wraith
#

this second part was weird in explaining it

high goblet
#

but yeah unfortunately it is just 1 exam at the end of the year

deft wraith
#

i don't know if it's really a good question either it's just algebra

high goblet
#

(you also get ur ranking in the year so ig only 1 exam means u can have an official ranking)

ornate blade
#

yeah it's this elite uni culture

high goblet
ornate blade
#

impressive

#

I found something you don't know about your uni

high goblet
#

but if u do well it's kinda nice knowing ur ranking lol

#

10th/259 :)

ornate blade
#

man like people are cracked

glad zinc
high goblet
high goblet
glad zinc
high goblet
#

ah right

#

the easier questions for BMO2 are comparable to the harder questions for BMO1

#

but yeah if u want easy IMO easy problems

glad zinc
#

Yeah, geometry always fucks me over no matter how easy though

high goblet
#

i suck at geo too

high goblet
glad zinc
#

A month until BMO1, I want to qualify for BMO2 this time, should I spam BMO1 papers? Or do something else to prepare

deft wraith
#

is there alpha and beta system in ia

glad zinc
high goblet
high goblet
#

i did 0 geometry questions in BMO1 and BMO2 in Y12

glad zinc
#

But y13 results dont even matter no?

#

Its after uni apps

high goblet
#

and then i proceeded to do a further 0 geometry questions in TST1,2,3 and 4

ornate blade
#

this is interesting, talking about accom

deft wraith
high goblet
glad zinc
#

Not british : (

glad zinc
#

And my country has a different weird system

high goblet
glad zinc
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Well yes but its a school in the UK

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not

high goblet
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do u hold a british passport?

glad zinc
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Nope

high goblet
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oh unfortunate

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is there any country u can represent?

glad zinc
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The country Im originally from, which I dont happen to live in and they have a weird system with little information online for qualifying for olympiads

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sooo yeah

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tough

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I guess Ill just do some undergrad olympiads

high goblet
deft wraith
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what even is an operator

glad zinc
high goblet
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it surprisingly doesn't require much theory

glad zinc
high goblet
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and if u do it ur smarter than 1/2 the chinese team and most of the south korean team

ornate blade
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interesting

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I was at a Jane Street event just today

ornate blade
deft wraith
ornate blade
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it could be something small such as tutoring secondary school students

high goblet
glad zinc
ornate blade
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basically they said the interview questions will be about getting you to explain your thinking, like Google or big tech if you know about those

deft wraith
glad zinc
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I see

deft wraith
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like explaining bit