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k a May Highlights and 2025 AoPS Online Class Information
jlacosta   0
May 1, 2025
May is an exciting month! National MATHCOUNTS is the second week of May in Washington D.C. and our Founder, Richard Rusczyk will be presenting a seminar, Preparing Strong Math Students for College and Careers, on May 11th.

Are you interested in working towards MATHCOUNTS and don’t know where to start? We have you covered! If you have taken Prealgebra, then you are ready for MATHCOUNTS/AMC 8 Basics. Already aiming for State or National MATHCOUNTS and harder AMC 8 problems? Then our MATHCOUNTS/AMC 8 Advanced course is for you.

Summer camps are starting next month at the Virtual Campus in math and language arts that are 2 - to 4 - weeks in duration. Spaces are still available - don’t miss your chance to have an enriching summer experience. There are middle and high school competition math camps as well as Math Beasts camps that review key topics coupled with fun explorations covering areas such as graph theory (Math Beasts Camp 6), cryptography (Math Beasts Camp 7-8), and topology (Math Beasts Camp 8-9)!

Be sure to mark your calendars for the following upcoming events:
[list][*]May 9th, 4:30pm PT/7:30pm ET, Casework 2: Overwhelming Evidence — A Text Adventure, a game where participants will work together to navigate the map, solve puzzles, and win! All are welcome.
[*]May 19th, 4:30pm PT/7:30pm ET, What's Next After Beast Academy?, designed for students finishing Beast Academy and ready for Prealgebra 1.
[*]May 20th, 4:00pm PT/7:00pm ET, Mathcamp 2025 Qualifying Quiz Part 1 Math Jam, Problems 1 to 4, join the Canada/USA Mathcamp staff for this exciting Math Jam, where they discuss solutions to Problems 1 to 4 of the 2025 Mathcamp Qualifying Quiz!
[*]May 21st, 4:00pm PT/7:00pm ET, Mathcamp 2025 Qualifying Quiz Part 2 Math Jam, Problems 5 and 6, Canada/USA Mathcamp staff will discuss solutions to Problems 5 and 6 of the 2025 Mathcamp Qualifying Quiz![/list]
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0 replies
jlacosta
May 1, 2025
0 replies
k i Adding contests to the Contest Collections
dcouchman   1
N Apr 5, 2023 by v_Enhance
Want to help AoPS remain a valuable Olympiad resource? Help us add contests to AoPS's Contest Collections.

Find instructions and a list of contests to add here: https://artofproblemsolving.com/community/c40244h1064480_contests_to_add
1 reply
dcouchman
Sep 9, 2019
v_Enhance
Apr 5, 2023
k i Zero tolerance
ZetaX   49
N May 4, 2019 by NoDealsHere
Source: Use your common sense! (enough is enough)
Some users don't want to learn, some other simply ignore advises.
But please follow the following guideline:


To make it short: ALWAYS USE YOUR COMMON SENSE IF POSTING!
If you don't have common sense, don't post.


More specifically:

For new threads:


a) Good, meaningful title:
The title has to say what the problem is about in best way possible.
If that title occured already, it's definitely bad. And contest names aren't good either.
That's in fact a requirement for being able to search old problems.

Examples:
Bad titles:
- "Hard"/"Medium"/"Easy" (if you find it so cool how hard/easy it is, tell it in the post and use a title that tells us the problem)
- "Number Theory" (hey guy, guess why this forum's named that way¿ and is it the only such problem on earth¿)
- "Fibonacci" (there are millions of Fibonacci problems out there, all posted and named the same...)
- "Chinese TST 2003" (does this say anything about the problem¿)
Good titles:
- "On divisors of a³+2b³+4c³-6abc"
- "Number of solutions to x²+y²=6z²"
- "Fibonacci numbers are never squares"


b) Use search function:
Before posting a "new" problem spend at least two, better five, minutes to look if this problem was posted before. If it was, don't repost it. If you have anything important to say on topic, post it in one of the older threads.
If the thread is locked cause of this, use search function.

Update (by Amir Hossein). The best way to search for two keywords in AoPS is to input
[code]+"first keyword" +"second keyword"[/code]
so that any post containing both strings "first word" and "second form".


c) Good problem statement:
Some recent really bad post was:
[quote]$lim_{n\to 1}^{+\infty}\frac{1}{n}-lnn$[/quote]
It contains no question and no answer.
If you do this, too, you are on the best way to get your thread deleted. Write everything clearly, define where your variables come from (and define the "natural" numbers if used). Additionally read your post at least twice before submitting. After you sent it, read it again and use the Edit-Button if necessary to correct errors.


For answers to already existing threads:


d) Of any interest and with content:
Don't post things that are more trivial than completely obvious. For example, if the question is to solve $x^{3}+y^{3}=z^{3}$, do not answer with "$x=y=z=0$ is a solution" only. Either you post any kind of proof or at least something unexpected (like "$x=1337, y=481, z=42$ is the smallest solution). Someone that does not see that $x=y=z=0$ is a solution of the above without your post is completely wrong here, this is an IMO-level forum.
Similar, posting "I have solved this problem" but not posting anything else is not welcome; it even looks that you just want to show off what a genius you are.

e) Well written and checked answers:
Like c) for new threads, check your solutions at least twice for mistakes. And after sending, read it again and use the Edit-Button if necessary to correct errors.



To repeat it: ALWAYS USE YOUR COMMON SENSE IF POSTING!


Everything definitely out of range of common sense will be locked or deleted (exept for new users having less than about 42 posts, they are newbies and need/get some time to learn).

The above rules will be applied from next monday (5. march of 2007).
Feel free to discuss on this here.
49 replies
ZetaX
Feb 27, 2007
NoDealsHere
May 4, 2019
Inequalities
toanrathay   0
18 minutes ago
Prove that the following inequality holds for all positive real numbers \( a, b, c \):
\[
\left( \frac{a}{b+c} + \frac{b}{c+a} \right) 
\left( \frac{b}{c+a} + \frac{c}{a+b} \right) 
\left( \frac{c}{a+b} + \frac{a}{b+c} \right) 
\geq \frac{(a+b+c)^2}{3(ab + bc + ca)}
\]

0 replies
toanrathay
18 minutes ago
0 replies
Painting Beads on Necklace
amuthup   46
N an hour ago by quantam13
Source: 2021 ISL C2
Let $n\ge 3$ be a fixed integer. There are $m\ge n+1$ beads on a circular necklace. You wish to paint the beads using $n$ colors, such that among any $n+1$ consecutive beads every color appears at least once. Find the largest value of $m$ for which this task is $\emph{not}$ possible.

Carl Schildkraut, USA
46 replies
amuthup
Jul 12, 2022
quantam13
an hour ago
Iran geometry
Dadgarnia   38
N an hour ago by cursed_tangent1434
Source: Iranian TST 2018, first exam day 2, problem 4
Let $ABC$ be a triangle ($\angle A\neq 90^\circ$). $BE,CF$ are the altitudes of the triangle. The bisector of $\angle A$ intersects $EF,BC$ at $M,N$. Let $P$ be a point such that $MP\perp EF$ and $NP\perp BC$. Prove that $AP$ passes through the midpoint of $BC$.

Proposed by Iman Maghsoudi, Hooman Fattahi
38 replies
Dadgarnia
Apr 8, 2018
cursed_tangent1434
an hour ago
hard problem (to me)
kjhgyuio   2
N an hour ago by kjhgyuio
........
2 replies
kjhgyuio
Apr 19, 2025
kjhgyuio
an hour ago
PE is bisector of BPC
goldeneagle   44
N an hour ago by cursed_tangent1434
Source: Iran TST 2012 -first day- problem 2
Consider $\omega$ is circumcircle of an acute triangle $ABC$. $D$ is midpoint of arc $BAC$ and $I$ is incenter of triangle $ABC$. Let $DI$ intersect $BC$ in $E$ and $\omega$ for second time in $F$. Let $P$ be a point on line $AF$ such that $PE$ is parallel to $AI$. Prove that $PE$ is bisector of angle $BPC$.

Proposed by Mr.Etesami
44 replies
goldeneagle
Apr 23, 2012
cursed_tangent1434
an hour ago
find question
mathematical-forest   9
N an hour ago by JARP091
Are there any contest questions that seem simple but are actually difficult? :-D
9 replies
mathematical-forest
May 29, 2025
JARP091
an hour ago
Interesting inequality
sqing   1
N an hour ago by Zok_G8D
Source: Own
Let $  a, b,c>0,b+c\geq 3a$. Prove that
$$ \sqrt{\frac{a}{b+c-a}}-\frac{ 2a^2-b^2-c^2}{(a+b)(a+c)}\geq \frac{2}{5}+\frac{1}{\sqrt 2}$$$$ \frac{3}{2}\sqrt{\frac{a}{b+c-a}}-\frac{ 2a^2-b^2-c^2}{(a+b)(a+c)}\geq \frac{2}{5}+\frac{3}{2\sqrt 2}$$
1 reply
sqing
Yesterday at 2:49 AM
Zok_G8D
an hour ago
Basic ideas in junior diophantine equations
Maths_VC   6
N 2 hours ago by Adywastaken
Source: Serbia JBMO TST 2025, Problem 3
Determine all positive integers $a, b$ and $c$ such that
$2$ $\cdot$ $10^a + 5^b = 2025^c$
6 replies
Maths_VC
May 27, 2025
Adywastaken
2 hours ago
$p|f(m+n) \iff p|f(m) + f(n)$ (IMO Shortlist 2007, N5)
orl   49
N 2 hours ago by blueprimes
Source: IMO Shortlist 2007, N5, AIMO 2008, TST 3, P3
Find all surjective functions $ f: \mathbb{N} \to \mathbb{N}$ such that for every $ m,n \in \mathbb{N}$ and every prime $ p,$ the number $ f(m + n)$ is divisible by $ p$ if and only if $ f(m) + f(n)$ is divisible by $ p$.

Author: Mohsen Jamaali and Nima Ahmadi Pour Anari, Iran
49 replies
orl
Jul 13, 2008
blueprimes
2 hours ago
Inequality in triangle
Nguyenhuyen_AG   2
N 2 hours ago by JARP091
Let $a,b,c$ be the lengths of the sides of a triangle. Prove that
\[\frac{1}{(a-4b)^2}+\frac{1}{(b-4c)^2}+\frac{1}{(c-4a)^2} \geqslant \frac{1}{ab+bc+ca}.\]
2 replies
Nguyenhuyen_AG
5 hours ago
JARP091
2 hours ago
Interesting inequality
sqing   2
N 2 hours ago by sqing
Source: Own
Let $ a,b,c\geq  0 , a^2+b^2+c^2 =3.$ Prove that
$$ a^4+ b^4+c^4+6abc\leq9$$$$ a^3+ b^3+  c^3+3( \sqrt{3}-1)abc\leq 3\sqrt 3$$
2 replies
sqing
Today at 2:54 AM
sqing
2 hours ago
Original Question #2
Siopao_Enjoyer   1
N 3 hours ago by Siopao_Enjoyer
Let x, y, and z be positive real numbers such that:

√x + √y + √z = 17/3
1/√x + 1/√y + 1/√z = 21/4

If xyz = 16/9, one of the variables will be rational while the other two will be irrational. What is the value of that rational number?
1 reply
Siopao_Enjoyer
3 hours ago
Siopao_Enjoyer
3 hours ago
[PMO17 Qualifying III.5] Roots a+2/a-2
LilKirb   1
N 3 hours ago by pooh123
Let $\alpha$, $\beta$, and $\gamma$ be the roots of $x^3 - 4x - 8 = 0.$ Find the numerical value of the expression:
\[\frac{\alpha + 2}{\alpha - 2} + \frac{\beta + 2}{\beta - 2} + \frac{\gamma + 2}{\gamma - 2}\]
1 reply
LilKirb
5 hours ago
pooh123
3 hours ago
2017 Mathirang Mathibay - Orals, Tier 2 Easy
elpianista227   2
N 3 hours ago by anduran
Let $M, S, A$ be the roots of the polynomial $f(x) = 127x^3 + 1729x + 8128$. Find $(M + S)^3 + (S+ A)^3 + (A + M)^3$
2 replies
elpianista227
6 hours ago
anduran
3 hours ago
Classic Invariant
Mathdreams   2
N Apr 12, 2025 by Tony_stark0094
Source: 2025 Nepal Mock TST Day 1 Problem 1

Prajit and Kritesh challenge each other with a marble game. In a bag, there are initially $2024$ red marbles and $2025$ blue marbles. The rules of the game are as follows:

Move: In each turn, a player (either Prajit or Kritesh) removes two marbles from the bag.

If the two marbles are of the same color, they are both discarded and a red marble is added to the bag.
If the two marbles are of different colors, they are both discarded and a blue marble is added to the bag.

The game continues by repeating the above move.

Prove that no matter what sequence of moves is made, the process always terminates with exactly one marble left. In addition, find the possible colors of the marble remaining.
2 replies
Mathdreams
Apr 10, 2025
Tony_stark0094
Apr 12, 2025
Classic Invariant
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G H BBookmark kLocked kLocked NReply
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Mathdreams
1472 posts
#1
Y by
Source: 2025 Nepal Mock TST Day 1 Problem 1

Prajit and Kritesh challenge each other with a marble game. In a bag, there are initially $2024$ red marbles and $2025$ blue marbles. The rules of the game are as follows:

Move: In each turn, a player (either Prajit or Kritesh) removes two marbles from the bag.

If the two marbles are of the same color, they are both discarded and a red marble is added to the bag.
If the two marbles are of different colors, they are both discarded and a blue marble is added to the bag.

The game continues by repeating the above move.

Prove that no matter what sequence of moves is made, the process always terminates with exactly one marble left. In addition, find the possible colors of the marble remaining.
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Lankou
1406 posts
#2
Y by
No matter the move, 2 marbles are discarded and one is added, therefore the number of marbles is going to follow the sequence $4049, 4048, 4047,...3, 2$ at this point a player will remove the 2 remaining marbles and add one. The game then stops.

The remaining marble can be red or blue
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Tony_stark0094
69 posts
#3 • 2 Y
Y by aidan0626, Lankou
observe that change in no of blue marbles $\equiv 0\ (mod\ 2)$
hence no of blue marbles always remain odd so the last remaining marble must be blue
This post has been edited 1 time. Last edited by Tony_stark0094, Apr 12, 2025, 6:41 AM
Reason: typo
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a