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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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All classes run 7:30pm-8:45pm ET/4:30pm - 5:45pm PT unless otherwise noted.

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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
Polynomial Factors
somebodyyouusedtoknow   2
N 9 minutes ago by KevinYang2.71
Source: San Diego Honors Math Contest 2025 Part II, Problem 2
Let $P(x)$ be a polynomial with real coefficients such that $P(x^n) \mid P(x^{n+1})$ for all $n \in \mathbb{N}$. Prove that $P(x) = cx^k$ for some real constant $c$ and $k \in \mathbb{N}$.
2 replies
somebodyyouusedtoknow
Apr 26, 2025
KevinYang2.71
9 minutes ago
Continuity of function and line segment of integer length
egxa   3
N 10 minutes ago by arzhang2001
Source: All Russian 2025 11.8
Let \( f: \mathbb{R} \to \mathbb{R} \) be a continuous function. A chord is defined as a segment of integer length, parallel to the x-axis, whose endpoints lie on the graph of \( f \). It is known that the graph of \( f \) contains exactly \( N \) chords, one of which has length 2025. Find the minimum possible value of \( N \).
3 replies
egxa
Apr 18, 2025
arzhang2001
10 minutes ago
Inspired by lgx57
sqing   2
N 12 minutes ago by sqing
Source: Own
Let $ a,b>0, a^4+ab+b^4=10  $. Prove that
$$ \sqrt{10}\leq a^2+ab+b^2 \leq 6$$$$ 2\leq a^2-ab+b^2 \leq  \sqrt{10}$$$$  4\sqrt{10}\leq 4a^2+ab+4b^2 \leq18$$$$  12<4a^2-ab+4b^2 \leq14$$
2 replies
+1 w
sqing
44 minutes ago
sqing
12 minutes ago
Number Theory Marathon!!!
starchan   433
N 17 minutes ago by EthanWYX2009
Source: Possibly Mercury??
Number theory Marathon
Let us begin
P1
433 replies
starchan
May 28, 2020
EthanWYX2009
17 minutes ago
Quadric porism
qwerty123456asdfgzxcvb   0
18 minutes ago
Source: I actually don't know whether this holds, but the application of Riemann-Hurwitz would make sense to some extent
Let $\mathcal{H}$ be a hyperboloid of one sheet and let $\mathcal{Q}$ be another quadric that intersects the hyperboloid at the curve $\mathcal{S}$. Let $P_1$ be a point on $\mathcal{S}$, and let $\ell_1$ be a line through $P_1$ in one specific ruling of the hyperboloid. Let this line intersect $\mathcal{S}$ again at $P_2$, now define $\ell_2$ to be the line through $P_2$ in the opposite ruling. Similarily define $P_3, P_4$. Prove that if $P_4=P_1$ then this is true for all initial choices of $P_1$.

.
0 replies
qwerty123456asdfgzxcvb
18 minutes ago
0 replies
Diophantine equation with elliptic curve
F_Xavier1203   2
N 24 minutes ago by kes0716
Source: 2022 Korea Winter Program Practice Test
Prove that equation $y^2=x^3+7$ doesn't have any solution on integers.
2 replies
F_Xavier1203
Aug 14, 2022
kes0716
24 minutes ago
a^2-bc square implies 2a+b+c composite
v_Enhance   39
N 25 minutes ago by SimplisticFormulas
Source: ELMO 2009, Problem 1
Let $a,b,c$ be positive integers such that $a^2 - bc$ is a square. Prove that $2a + b + c$ is not prime.

Evan o'Dorney
39 replies
v_Enhance
Dec 31, 2012
SimplisticFormulas
25 minutes ago
Vincent's Theorem
EthanWYX2009   0
26 minutes ago
Source: Vincent's Theorem
Let $p(x)$ be a real polynomial of degree $\deg(p)$ that has only simple roots. It is possible to determine a positive quantity $\delta$ so that for every pair of positive real numbers $a$, $b$ with ${\displaystyle |b-a|<\delta }$, every transformed polynomial of the form $${\displaystyle f(x)=(1+x)^{\deg(p)}p\left({\frac {a+bx}{1+x}}\right)}$$has exactly $0$ or $1$ sign variations.
0 replies
EthanWYX2009
26 minutes ago
0 replies
JBMO Shortlist 2019 N5
Steve12345   11
N 30 minutes ago by MR.1
Find all positive integers $x, y, z$ such that $45^x-6^y=2019^z$

Proposed by Dorlir Ahmeti, Albania
11 replies
Steve12345
Sep 12, 2020
MR.1
30 minutes ago
polonomials
Ducksohappi   1
N 37 minutes ago by top1vien
$P\in \mathbb{R}[x] $ with even-degree
Prove that there is a non-negative integer k such that
$Q_k(x)=P(x)+P(x+1)+...+P(x+k)$
has no real root
1 reply
Ducksohappi
Today at 8:36 AM
top1vien
37 minutes ago
Inspired by Bet667
sqing   3
N an hour ago by sqing
Source: Own
Let $ a,b $ be a real numbers such that $a^3+kab+b^3\ge a^4+b^4.$Prove that
$$1-\sqrt{k+1} \leq  a+b\leq 1+\sqrt{k+1} $$Where $ k\geq 0. $
3 replies
sqing
2 hours ago
sqing
an hour ago
Geometry marathon
HoRI_DA_GRe8   846
N an hour ago by ItzsleepyXD
Ok so there's been no geo marathon here for more than 2 years,so lets start one,rules remain same.
1st problem.
Let $PQRS$ be a cyclic quadrilateral with $\angle PSR=90°$ and let $H$ and $K$ be the feet of altitudes from $Q$ to the lines $PR$ and $PS$,.Prove $HK$ bisects $QS$.
P.s._eeezy ,try without ss line.
846 replies
HoRI_DA_GRe8
Sep 5, 2021
ItzsleepyXD
an hour ago
Find all functions $f$ is strictly increasing : \(\mathbb{R^+}\) \(\rightarrow\)
guramuta   0
an hour ago
Find all functions $f$ is strictly increasing : \(\mathbb{R^+}\) \(\rightarrow\) \(\mathbb{R^+}\) such that:
i) $f(2x)$ \(\geq\) $2f(x)$
ii) $f(f(x)f(y)+x) = f(xf(y)) + f(x) $
0 replies
+1 w
guramuta
an hour ago
0 replies
Partitioning coprime integers to arithmetic sequences
sevket12   3
N an hour ago by quacksaysduck
Source: 2025 Turkey EGMO TST P3
For a positive integer $n$, let $S_n$ be the set of positive integers that do not exceed $n$ and are coprime to $n$. Define $f(n)$ as the smallest positive integer that allows $S_n$ to be partitioned into $f(n)$ disjoint subsets, each forming an arithmetic progression.

Prove that there exist infinitely many pairs $(a, b)$ satisfying $a, b > 2025$, $a \mid b$, and $f(a) \nmid f(b)$.
3 replies
sevket12
Feb 8, 2025
quacksaysduck
an hour ago
parallel and perpendicular related, starting with a cyclic ABCD
parmenides51   1
N Sep 21, 2020 by DNCT1
Source: 2017 Saudi Arabia IMO TST III p2
Let $ABCD$ be a quadrilateral inscribed a circle $(O)$. Assume that $AB$ and $CD$ intersect at $E, AC$ and $BD$ intersect at $K$, and $O$ does not belong to the line $KE$. Let $G$ and $H$ be the midpoints of $AB$ and $CD$ respectively. Let $(I)$ be the circumcircle of the triangle $GKH$. Let $(I)$ and $(O)$ intersect at $M, N$ such that $MGHN$ is convex quadrilateral. Let $P$ be the intersection of $MG$ and $HN,Q$ be the intersection of $MN$ and $GH$.
a) Prove that $IK$ and $OE$ are parallel.
b) Prove that $PK$ is perpendicular to $IQ$.
1 reply
parmenides51
Jul 27, 2020
DNCT1
Sep 21, 2020
parallel and perpendicular related, starting with a cyclic ABCD
G H J
Source: 2017 Saudi Arabia IMO TST III p2
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parmenides51
30651 posts
#1
Y by
Let $ABCD$ be a quadrilateral inscribed a circle $(O)$. Assume that $AB$ and $CD$ intersect at $E, AC$ and $BD$ intersect at $K$, and $O$ does not belong to the line $KE$. Let $G$ and $H$ be the midpoints of $AB$ and $CD$ respectively. Let $(I)$ be the circumcircle of the triangle $GKH$. Let $(I)$ and $(O)$ intersect at $M, N$ such that $MGHN$ is convex quadrilateral. Let $P$ be the intersection of $MG$ and $HN,Q$ be the intersection of $MN$ and $GH$.
a) Prove that $IK$ and $OE$ are parallel.
b) Prove that $PK$ is perpendicular to $IQ$.
Z K Y
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DNCT1
235 posts
#2 • 1 Y
Y by amar_04
solution part a
solution part b
Attachments:
This post has been edited 3 times. Last edited by DNCT1, Sep 21, 2020, 6:35 PM
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