#competition-math

70351 messages · Page 71 of 71 (latest)

clever galleon
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Wait wdym?

silver forge
clever galleon
silver forge
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so would you like another one

clever galleon
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Yeah sure

silver forge
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ok

strong latch
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oh damn

silver forge
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I dont think a lotta ppl solved this

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btw i only give questions which i have solved soif u have any q i can explain

clever galleon
clever galleon
silver forge
neon summit
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nuh uh

clever galleon
neon summit
silver forge
neon summit
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at least 12

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oh it's multiple choice

silver forge
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r u referring to the number of ppl who solved it or the answer

neon summit
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hmmm

neon summit
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I'm prolly stupid tho

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hard to say I can't divide by 10 in my head

silver forge
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Lemme find my answer

inland totem
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is it ||c||?

neon summit
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I should rly relearn how to do stuff in my head real fast

silver forge
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that was quick plens

silver forge
neon summit
silver forge
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also u shud blur ur answers to not spoil it forothers

inland totem
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think wen sent it

silver forge
neon summit
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I was like 67.89% sure now I'm pretty sure it's 100%

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mm

silver forge
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how yall mental math so fast

neon summit
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u got any comp calc problems

silver forge
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it took me like five minutes

silver forge
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but i can give u a hard one

neon summit
silver forge
neon summit
silver forge
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tis is not intuitively obvious

neon summit
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I can't load it

inland totem
neon summit
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ye it's not loading for me

silver forge
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@inland totem u shud watch takopis original sin

silver forge
neon summit
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DON'T DO IT

inland totem
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ok

silver forge
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u watched it?

neon summit
silver forge
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soooo peak

inland totem
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uhh i saw one this morning

silver forge
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but sooooo sad

inland totem
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it was cool

neon summit
inland totem
neon summit
inland totem
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idk if this quals as comp calc

silver forge
neon summit
silver forge
neon summit
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huh

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am on phone

inland totem
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hmm

silver forge
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just close and reopen the app

inland totem
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alr wait i havs smth to do rn

silver forge
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Your phone gets tired too yk

silver forge
neon summit
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is it ||B||

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it's probably intuitive but I don't know series

inland totem
neon summit
neon summit
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uh

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yeah not a pretty number

inland totem
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ye u can turn into a riemann sum

neon summit
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glad I never studied that(severe larp detected)

inland totem
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hmm

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i larp a lot of things

silver forge
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lol larping in math is the funniest

neon summit
# silver forge

27>x>7
consider right triangle sides wherein the hypotenuse would be greater than
so we get x^2>10^2+17^2 and x^2+10^2>17^2 giving us x values of 19-27 and 9 giving us 208 AND it's not in the choices I'm so smart

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I'm the goat

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what is 17^2 anw

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oh it's 289, not 189

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289

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🤦

ruby bramble
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I'm building numberthon (numberthon.com) — what’s the best part of competition math for you guys?

inland totem
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the geometry problems

ruby bramble
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wdym

silver forge
ruby bramble
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oh, ok

neon summit
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looks weird

silver forge
neon summit
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ah hypotenuse larger

neon summit
silver forge
inland totem
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i love bashing

silver forge
neon summit
neon summit
inland totem
# silver forge

split into cases where x is the longest side and then 17 is the longest side

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i'm pretty sure it's ||e||

neon summit
inland totem
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bc 17 is alr a side

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and 17 > 10

neon summit
inland totem
neon summit
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yeah I got the karma I deserved, I was walking bear foot in the dark and stepped on a Lego 🥀

neon summit
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how would I know the set it just hurt like hell

idle aspen
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Fair

silver forge
silver forge
neon summit
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I'm confused

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my answer was 208 I was wondering why I was wrong I got the wrong number and did 189-100 not 289-100

clever galleon
silver forge
clever galleon
silver forge
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corrects

clever galleon
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Thanks 😄

silver forge
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even nautilus got confused

clever galleon
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For reading through that mess

clever galleon
silver forge
unreal spruce
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😭

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area cant be negative anyway

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so like

silver forge
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kinda pointless

unreal spruce
clever galleon
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For specifying it’s..oh yeah right it can’t be non degenerate

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Uhh okay i got…from the triangle inequalities it’s 323

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Guys I didn’t use the first 2 parts tho…

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Anyone wanna read my working?

silver forge
clever galleon
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Wait I’ll send

silver forge
inland totem
clever galleon
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It’s wrong?

inland totem
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uhmm yeah

clever galleon
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Oh yeah right.

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Then I think it’s 161?

silver forge
clever galleon
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Uhh might not be readable. I wrote the last few steps on another page

clever galleon
silver forge
clever galleon
rotund venture
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hI

silver forge
clever galleon
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Oh yeah it’s E

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22r

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224*

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lol i totally forgot about this case

silver forge
clever galleon
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Like my brain warped around “either x is opp acute angle or obtuse” and forgot to consider this

clever galleon
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But no calc I’m just learning calc

silver forge
clever galleon
silver forge
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The last one was kinda annoying

clever galleon
# silver forge u do math coaching?

No JEE coaching. It’s like an engineering entrance in India (yes many Indian parents have a very binary view on careers- either you become a doctor or an engineer)

clever galleon
silver forge
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Engineering coaching is a new concept for me

clever galleon
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So like this foundation course is like- super intensive so they’re spoon feeding us calculus with 0 proofs

clever galleon
clever galleon
clever galleon
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To say the least

silver forge
clever galleon
silver forge
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all roads lead to one (collatz conjecture)

clever galleon
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But like sometimes my parents try to make me abandon Olympiads…but I don’t want to so they said I’m gonna have to do both

clever galleon
neon summit
clever galleon
inland totem
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why are we trying to solve the collatz conjecture at 10 years old 😭

clever galleon
inland totem
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oh ye i did too

clever galleon
inland totem
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but didnt it explicitly say "do not try doing this problem, do some normal math for once" or smth

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hmm

clever galleon
silver forge
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what would the first step even be

clever galleon
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Like seeing if there was a specific structure on how each of them come back to one

silver forge
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Youd need statisticsl analysis and a bit of probability theory minimum

neon summit
# silver forge harharhar

circle rectangle thing, uhh probably ||D||, it's a bit shorter and there's no choice 3950
quarter circle's a nice one
don't think id's possible for the grasshopper to do that

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hard to imagine on phone mm

clever galleon
clever galleon
neon summit
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pfft

clever galleon
neon summit
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I'm lazy

neon summit
neon summit
# silver forge harharhar

10 10sqrt5
triangle base is 10sqrt5-10
10sqrt5-20=base of really small triangle, 30-10sqrt 5 is base of the larger shaded so now u can do maht to do 100(14-6sqrt5)+50(9-4sqrt5) which I'm not calculating thx

clever galleon
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Uhhh i think the answer is ||option d 4000|| but I’m not sure

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For the first 3 circles one

tiny eagle
clever galleon
tiny eagle
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Will send sol later

clever galleon
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||using approximation for root 15 as 38.7 (yes i used a calculator) I got this…||

unreal spruce
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liek

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like*

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forbidden or sum

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😭

silver forge
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mental mathing is good

unreal spruce
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u can mental math roots?

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thats

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intersting

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smh

stone canopy
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you don’t need to write out approximate decimal places i assume

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so all it is is just dividing a number by primes until you get all primes

unreal spruce
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oh

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i didnt know

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u can do that

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lowk

silver forge
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babylonian method

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not mental math

unreal spruce
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never heard of it

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lowk

silver forge
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also i dont usually mental math roots

unreal spruce
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i am not really into olympiad maths

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anyway

silver forge
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i mean like with addition stuff

unreal spruce
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so most of this is just gibbrish to me

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lol

silver forge
silver forge
unreal spruce
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like in my free time

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anything thats not calc related tho

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and trig

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related

silver forge
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i only let myself do it after i do my textbook work

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so it feels like a reward

unreal spruce
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noice

inland totem
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<@&268886789983436800>

ruby bramble
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what do you guys like abt competition math?

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(I am asking bc I'm making a competitive math platform called numberthon.com)

echo ocean
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Now get as many combi problem as possible into the platform, people will love it, trust me

silver forge
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they challenge me and force me to use new methods that might not be new to the world but is new to me

thorny tusk
clever galleon
# unreal spruce u can mental math roots?

They asked for closest, and we know it’s less than 4, so like, so basically we know its less than 4 (so less than 4000) but not like very less, so guessing 3950 without finding root is possible. But like there’s actually a long division method to find square root (digit by digit algorithm i think) which you can do in ur head with practice

ashen hatch
clever galleon
inland totem
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i mean some comps like mathcounts also prioritize speed

clever galleon
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I guess?

inland totem
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hmm ye fair

clever galleon
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I first got 4000 but then corrected it

silver forge
clever galleon
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Idk how I got 4000 first

silver forge
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3950 is correct

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*i think

clever galleon
clever galleon
silver forge
clever galleon
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I just got out of the test (it was online)

silver forge
clever galleon
# silver forge yay how did u do

It was like moderately difficult, but the results come out tomorrow afternoon after the teachers check the results (like it was McQ but there’s like a check before they publish the results) so yeah

clever galleon
neon summit
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I can do 2 digits but 3 digits is preferrable cuz of the amount of 10s

grim brook
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its the key to larp

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my friend tries to solve as many things as he can with combinatorics to maximize how sophisticated he looks

neon summit
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combinatorics can't possibly be that hard there's only 3 formulas

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3 formulas everyone refuses to learn and make sense of

quaint nexus
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Im trying to figure a way to do these without groking it out

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I know /varnull is (a + b + c)^2- 3(ab + bc + ac), but not sure that helps

ivory ember
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Elementary symmetric polynomials my beloved

quaint nexus
spark scaffold
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54 use pascal triangle

quaint nexus
spark scaffold
quaint nexus
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Im aware of the binomial theorem for the coefficient but this implies actually working it out entirely?

spark scaffold
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That’s what I want to know

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I would solve for the LHS

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Then to compare

quaint nexus
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Yeah that’s how I did it; simplify both sides a bit and it’s easy to show

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Just not very elegant

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Although

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For context it’s from an algebra book’s chapter review on polynomials and factoring, so it’s entirely possible it’s just meant to impart a ridiculous amount of computation. Just caught my eye and I was curious

restive anvil
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Like perms combs and binomial expansion u mean?

neon summit
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what're those

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(I refused to learn them)

neon summit
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omg calc

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nabla reference

clever galleon
unreal spruce
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I'm quite puzzled

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Idk how to solve it

heady summit
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Does anyone have any moderately easy number theory problem? I'm getting kinda bored

vernal axle
clever galleon
unreal spruce
vernal axle
inland totem
dapper meadow
dapper meadow
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my bad

clever galleon
dapper meadow
clever galleon
dapper meadow
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No no just in general

clever galleon
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Lengthy calculations do that

dapper meadow
# vernal axle Of course it is this

I was planning on splitting it between even and odd but then couldn’t do odd. I’m new to number theory and proofs in general, could you help me out

vernal axle
tiny eagle
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Progressing from there should be easy

inland totem
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i did this with ||fermat's little theorem||

vernal axle
ruby bramble
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What do you guys think abt this competitive math website that I made?: https://numberthon.com/ Any suggestions on features to add (it aims to be the "chess.com of math")?

Numberthon

Challenge your mind and climb the ranks in Numberthon, the ultimate platform for competitive math enthusiasts. Solve problems faster than your opponent to win,

inland totem
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i quite like the ui and design tbh

ruby bramble
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Thanks!

quaint nexus
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Also, for what it’s worth, 52 is pretty easy if you just multiply out the RHS

quaint nexus
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As far as I’ve tried, there doesn’t seem to be a way to ‘deduce’ the RHS from the LHS in 52. Best I can do is something like this (basically equates to: “oh! Notice this occurs, which I honestly think is BS when including on a problem set, but I guess it makes the authors feel cool)

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Also, in my opinion, the only reason anyone would even bother trying to figure this out is because the factored form is already given. I highly doubt anyone would recognize/care for this “in the wild”

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There are theorems in abstract algebra regarding symmetric polynomials, I just don’t see what the use of including them here is- especially when no mention or even reference is made to those notions/results elsewhere

unreal spruce
grim brook
quaint nexus
quaint nexus
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Yeah I mean it’s kind of upsetting to me when stuff like this comes up; like this is a result that is usually shown using galois theory; if you’re going to include these, say something about that so people aren’t rereading the chapter and rechecking their work because they’re under the impression they can’t solve it because of some fundamental misunderstanding

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Why are you tagging me?

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You seem to think because no one else is responding right now that no one else will respond at all

tawdry furnace
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@silver forge pls dont make irrelevant posts in topic channels

shy raptor
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And you can discontinue speaking for a longer time, considering your history...

ivory ember
# quaint nexus As far as I’ve tried, there doesn’t seem to be a way to ‘deduce’ the RHS from th...

Yeah this is one of those "classic" facts that's normally proven by expansion. Ig you could also say that
$$(x+y)^3=x^3+y^3+3xy(x+y) \implies x^3+y^3=(x+y)^3-3xy(x+y),$$
and so
\begin{align*}
a^3+b^3+c^3-3abc &= [(a+b)^3-3ab(a+b)]+c^3-3abc \
&= [(a+b)^3+c^3]-3ab(a+b+c) \
&= (a+b+c)((a+b)^2-(a+b)c+c^2)-3ab(a+b+c) \
&= (a+b+c)[(a+b)^2-(a+b)c+c^2-3ab] \
&= (a+b+c)(a^2+b^2+c^2-ab-bc-ca).
\end{align*}

You can also inspect that setting $a=-b-c$ forces the expression to be zero, so $a+b+c$ is a factor and then you can do division. (I've never done this, so it probably sucks.) \

Fwiw, this is precisely the determinant of a $3 \times 3$ circulant matrix:
$$\begin{vmatrix} a & b & c \ c & a & b \ b & c & a \end{vmatrix}=a^3+b^3+c^3-3abc,$$
So the factorisation makes it easier to find the eigenvalues. (Note that circulant matrices are common in digitial signal processing.) \

In a sense, you could also use this to prove the identity. Because
$$\begin{vmatrix} a & b & c \ c & a & b \ b & c & a \end{vmatrix}=\begin{vmatrix} a+b+c & b & c \ a+b+c & a & b \ a+b+c & c & a \end{vmatrix}=(a+b+c) \underbrace{\begin{vmatrix} 1 & b & c \ 1 & a & b \ 1 & c & a \end{vmatrix}}_{a^2+b^2+c^2-ab-bc-ca},$$
and so
$$a^3+b^3+c^3-3abc=(a+b+c)(a^2+b^2+c^2-ab-bc-ca).$$

gilded haloBOT
#

Civil Service Pigeon

ivory ember
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rough first draft, so you could probably try to refine these proofs as an exercise (especially the first one)

quaint nexus
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I guess I was looking for a way to factor the LHSs to obtain the RHSs, which I don’t think is possible unless you’re aware of decomposing symmetric polynomials in terms of elementary symmetric polynomials- which no one reading a college algebra book to learn from would have any idea about or be able to deduce

neon summit
inland totem
neon summit
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wait

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hmmm

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yeah it is I'm prolly just dunv

gilded haloBOT
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Civil Service Pigeon

neon summit
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243 is 3^5

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I know ur in there euler I just don't wanna think about it

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||what I'm thinking is that either x or y must have a common factor with 243 so basically just all numbers divisible by 3 and stuff and then the gcd is any factor of 243 prolly||

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but I'm prolly approaching wrong

ivory ember
neon summit
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247
hmm

young halo
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||Like on rearranging we get that gcd(x,y) will divide 243 ( since gcd divides LCM always)
Idk whether this will be a relevant idea
So you can now look into possible gcds||

sinful flicker
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is the answer ||2668||?

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yay

ivory ember
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wait where tf did I read ||2666||

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I was like "nooooo why are you off by 2 bearlain"

ivory ember
ivory ember
ivory ember
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reading is hard

sinful flicker
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fr

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i did it by
||letting 3^a = gcd and 3^b = xy/gcd²+1 and since a + b = 5 i solved for every possibility of x and y|| is there a faster way

ivory ember
gilded haloBOT
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Civil Service Pigeon

ivory ember
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that's really the only way I can think of making this more efficient

ivory ember
# sinful flicker how tho

Let $\gcd(x,y)=3^a$ and let $x=3^a u$, $y=3^a v$ for $\gcd(u,v)=1$. Then, $\operatorname{lcm}(x,y)=3^a uv$. Hence,
$$3^a uv-3^a=243 \implies 3^a (uv-1)=3^5.$$
So, $uv-1=3^{5-a}$. \

But since $u$, $v$ are coprime, every prime power in the factorisation of $3^{5-a}+1$ must go entirely to $u$ or $v$. This means the number of ordered coprime positive pairs $(u,v)$ is $2^{\omega(3^{5-a}+1)}$. At this point, you can simply run over $a=0$, $1$, $2$, $3$, $4$, $5$ by finding the pairs $(u,v)$ and multiplying them by $3^a$ since
$$x+y=3^a u+3^a v=3^a (u+v).$$

gilded haloBOT
#

Civil Service Pigeon

sinful flicker
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noo training my reading comprehension

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ok ima read

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oh wait thats what i did basically i think

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cool

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what is $\omega$ though

gilded haloBOT
clever galleon
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Anyone wants a moderate geometry problem I’ve solved?

sinful flicker
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or i think so im not too sure

ivory ember
sinful flicker
clever galleon
clever galleon
# clever galleon

I might be busy for some time so I’ll not be replying, but i have solved it and i can help whoever needs help

sinful flicker
# ivory ember <:opencry:586078614865444865>

oh god theres more https://en.wikipedia.org/wiki/Arithmetic_function
and it doesnt help that the sum and product symbol are both greek too

In number theory, an arithmetic, arithmetical, or number-theoretic function is generally any function whose domain is the set of positive integers and whose range is a subset of the complex numbers. Hardy & Wright include in their definition the requirement that an arithmetical function "expresses some arithmetical property of n". There is a lar...

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number theory might as well have been made in greece atp

ivory ember
# clever galleon

$$x+\frac{2\Delta}{x}=y+\frac{2\Delta}{y} \implies x-y=2\Delta \left(\frac{x-y}{xy} \right) \implies \Delta=\frac{1}{2}xy.$$
This implies that we have a right triangle with legs $60$, $63$, and so the longest side of the triangle has length $\sqrt{60^2+63^2}=3 \cdot 29=\boxed{87}$.

gilded haloBOT
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Civil Service Pigeon

clever galleon
clever galleon