Plan ahead for the next school year. Schedule your class today!

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k a July Highlights and 2025 AoPS Online Class Information
jwelsh   0
Jul 1, 2025
We are halfway through summer, so be sure to carve out some time to keep your skills sharp and explore challenging topics at AoPS Online and our AoPS Academies (including the Virtual Campus)!

[list][*]Over 60 summer classes are starting at the Virtual Campus on July 7th - check out the math and language arts options for middle through high school levels.
[*]At AoPS Online, we have accelerated sections where you can complete a course in half the time by meeting twice/week instead of once/week, starting on July 8th:
[list][*]MATHCOUNTS/AMC 8 Basics
[*]MATHCOUNTS/AMC 8 Advanced
[*]AMC Problem Series[/list]
[*]Plus, AoPS Online has a special seminar July 14 - 17 that is outside the standard fare: Paradoxes and Infinity
[*]We are expanding our in-person AoPS Academy locations - are you looking for a strong community of problem solvers, exemplary instruction, and math and language arts options? Look to see if we have a location near you and enroll in summer camps or academic year classes today! New locations include campuses in California, Georgia, New York, Illinois, and Oregon and more coming soon![/list]

MOP (Math Olympiad Summer Program) just ended and the IMO (International Mathematical Olympiad) is right around the corner! This year’s IMO will be held in Australia, July 10th - 20th. Congratulations to all the MOP students for reaching this incredible level and best of luck to all selected to represent their countries at this year’s IMO! Did you know that, in the last 10 years, 59 USA International Math Olympiad team members have medaled and have taken over 360 AoPS Online courses. Take advantage of our Worldwide Online Olympiad Training (WOOT) courses
and train with the best! Please note that early bird pricing ends August 19th!
Are you tired of the heat and thinking about Fall? You can plan your Fall schedule now with classes at either AoPS Online, AoPS Academy Virtual Campus, or one of our AoPS Academies around the US.

Our full course list for upcoming classes is below:
All classes start 7:30pm ET/4:30pm PT unless otherwise noted.

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0 replies
jwelsh
Jul 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
Polynomials
Roots_Of_Moksha   7
N 19 minutes ago by vanstraelen
The polynomial $x^3 - 3(1+\sqrt{2})x^2 + (6\sqrt{2}-55)x -(7+5\sqrt{2})$ has three distinct real roots $\alpha$, $\beta$ and $\gamma$. The polynomial $p(x)=x^3+ax^2+bx+c$ has roots $\sqrt[3]{\alpha}$, $\sqrt[3]{\beta}$, $\sqrt[3]{\gamma}$. Find the integer closest to $a^2 + b^2 + c^2$.
Answer
7 replies
Roots_Of_Moksha
Jul 20, 2025
vanstraelen
19 minutes ago
Angles in a quadrilateral (beautiful and almost famous)
Johann Peter Dirichlet   11
N 35 minutes ago by Fly_into_the_sky
Source: Problem 4, Brazil MO 1993
$ABCD$ is a convex quadrilateral with
\[\angle BAC = 30^\circ \]\[\angle CAD = 20^\circ\]\[\angle ABD = 50^\circ\]\[\angle DBC = 30^\circ\]
If the diagonals intersect at $P$, show that $PC = PD$.
11 replies
Johann Peter Dirichlet
Mar 18, 2006
Fly_into_the_sky
35 minutes ago
fixed point for circumcircle of AQR, PQ//AB, PR //AC
parmenides51   2
N an hour ago by SuperBarsh
Source: Mexican Geometry Olympiad 2014 (OMG) - La Geometrense p4 https://artofproblemsolving.com/community/c2664039_2014_mexican_geometr
Let $ABC$ be a triangle and $G$ its centroid. A point $P$ is taken on segment $BC$. Take points $Q$ and $R$ on the sides $AC$ and $AB$ respectively, so that $PQ \parallel AB$ and $PR \parallel AC$. Show that as $P$ varies in segment $BC$, the circumcircle of triangle $AQR$ passes through a fixed point $X$.
2 replies
parmenides51
Nov 28, 2021
SuperBarsh
an hour ago
Inequalities
sqing   10
N an hour ago by DAVROS
Let $ a,b> 0 $ and $2a+2b+ab=5. $ Prove that
$$ \frac{a^4}{b^4}+\frac{1}{a^4}+42ab-a^4\geq  43$$$$ \frac{a^5}{b^5}+\frac{1}{a^5}+64ab-a^5\geq  65$$$$ \frac{a^6}{b^6}+\frac{1}{a^6}+90ab-a^6\geq  91$$$$ \frac{a^7}{b^7}+\frac{1}{a^7}+121ab-a^7\geq  122$$
10 replies
sqing
May 28, 2025
DAVROS
an hour ago
no integers on the interval
MathLover_ZJ   6
N an hour ago by grimreaper44
Source: 2022 China Southeast Grade 10 P7
Let $a,b$ be positive integers.Prove that there are no positive integers on the interval $\bigg[\frac{b^2}{a^2+ab},\frac{b^2}{a^2+ab-1}\bigg)$.
6 replies
MathLover_ZJ
Aug 3, 2022
grimreaper44
an hour ago
Bai lu zhou Academy Problem
David-Vieta   8
N an hour ago by grimreaper44
Source: 2022 China Southeast Grade 10 P3 and 11 P4
If $x_i$ is an integer greater than 1, let $f(x_i)$ be the greatest prime factor of $x_i,x_{i+1} =x_i-f(x_i)$ ($i\ge 0$ and i is an integer).
(1) Prove that for any integer $x_0$ greater than 1, there exists a natural number$k(x_0)$, such that $x_{k(x_0)+1}=0$
Grade 10: (2) Let $V_{(x_0)}$ be the number of different numbers in $f(x_0),f(x_1),\cdots,f(x_{k(x_0)})$. Find the largest number in $V(2),V(3),\cdots,V(781)$ and give reasons.
Note: Bai Lu Zhou Academy was founded in 1241 and has a history of 781 years.
Grade 11: (2) Let $V_{(x_0)}$ be the number of different numbers in $f(x_0),f(x_1),\cdots,f(x_{k(x_0)})$. Find the largest number in $V(2),V(3),\cdots,V(2022)$ and give reasons.
8 replies
David-Vieta
Aug 2, 2022
grimreaper44
an hour ago
Find the number
Thanhdoan1   3
N an hour ago by CuriousMathBoy72
Find all the positive number x such that x^3+3^x is a square.
3 replies
Thanhdoan1
Yesterday at 2:39 PM
CuriousMathBoy72
an hour ago
FE : f(x+f(y))+f(y+f(x))=f(f(2x)+2y)
Valjeanpi   3
N an hour ago by Bridgeon
Find all surjective fonctions $f:\mathbb R ^+ \backslash\{0\}\rightarrow \mathbb R ^+ \backslash\{0\}$ verifying :
$$f(x+f(y))+f(y+f(x))=f(f(2x)+2y)$$for all $x,y\in \mathbb R ^+ \backslash\{0\} $
3 replies
Valjeanpi
Feb 15, 2023
Bridgeon
an hour ago
computational, cyclic ABCD
parmenides51   1
N an hour ago by SuperBarsh
Source: Mexican Geometry Olympiad 2014 (OMG) - La Geometrense p2 https://artofproblemsolving.com/community/c2664039_2014_mexican_geometr
Quadrilateral $ABCD$ is inscribed in a circle of radius $ 1$, such that the diagonal $AC$ is a diameter and $BD=AB$. Diagonals intersect at $P$. It is known that $PC=\frac25$ . What is the length of side $CD$?
1 reply
parmenides51
Nov 28, 2021
SuperBarsh
an hour ago
orang NT
KevinYang2.71   26
N an hour ago by blug
Source: ISL 2024 N1
Find all positive integers $n$ with the following property: for all positive divisors $d$ of $n$, we have $d+1\mid n$ or $d+1$ is prime.
26 replies
KevinYang2.71
Jul 16, 2025
blug
an hour ago
Combinatorics
jawadkaleem   2
N an hour ago by Alphabeta123
Michel starts with the string HMMT.
An operation consists of either replacing an occurrence of H with HM, replacing an
occurrence of MM with MOM, or replacing an occurrence of T with MT. For example,
the two strings that can be reached after one operation are HMMMT and HMOMT.
Compute the number of distinct strings Michel can obtain after exactly 10 operation
2 replies
jawadkaleem
Jul 2, 2025
Alphabeta123
an hour ago
Find the value of angle C
markosa   10
N an hour ago by wisewigglyjaguar
Given a triangle ABC with base BC

angle B = 3x
angle C = x
AP is the bisector of base BC (i.e.) BP = PC
angle APB = 45 degrees

Find x

I know there are multiple methods to solve this problem using cosine law, coord geo
But is there any pure geometrical solution?
10 replies
markosa
3 hours ago
wisewigglyjaguar
an hour ago
An easy geometry in Taiwan TST
Li4   8
N 2 hours ago by Aiden-1089
Source: 2022 Taiwan TST Round 3 Independent Study 1-G
Let $ABC$ be an acute triangle with orthocenter $H$ and circumcircle $\Omega$. Let $M$ be the midpoint of side $BC$. Point $D$ is chosen from the minor arc $BC$ on $\Gamma$ such that $\angle BAD = \angle MAC$. Let $E$ be a point on $\Gamma$ such that $DE$ is perpendicular to $AM$, and $F$ be a point on line $BC$ such that $DF$ is perpendicular to $BC$. Lines $HF$ and $AM$ intersect at point $N$, and point $R$ is the reflection point of $H$ with respect to $N$.

Prove that $\angle AER + \angle DFR = 180^\circ$.

Proposed by Li4.
8 replies
Li4
Apr 27, 2022
Aiden-1089
2 hours ago
combinatorics
kjhgyuio   1
N 2 hours ago by Alphabeta123
........
1 reply
kjhgyuio
Jun 25, 2025
Alphabeta123
2 hours ago
Find function
trito11   3
N May 14, 2025 by jasperE3
Find $f:\mathbb{R^+} \to \mathbb{R^+} $ such that
i) f(x)>f(y) $\forall$ x>y>0
ii) f(2x)$\ge$2f(x)$\forall$x>0
iii)$f(f(x)f(y)+x)=f(xf(y))+f(x)$$\forall$x,y>0
3 replies
trito11
Nov 11, 2019
jasperE3
May 14, 2025
Find function
G H J
G H BBookmark kLocked kLocked NReply
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trito11
199 posts
#1 • 2 Y
Y by Adventure10, PikaPika999
Find $f:\mathbb{R^+} \to \mathbb{R^+} $ such that
i) f(x)>f(y) $\forall$ x>y>0
ii) f(2x)$\ge$2f(x)$\forall$x>0
iii)$f(f(x)f(y)+x)=f(xf(y))+f(x)$$\forall$x,y>0
This post has been edited 1 time. Last edited by trito11, Nov 11, 2019, 3:46 AM
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Mathzeus1024
1073 posts
#2 • 2 Y
Y by rachelcassano, PikaPika999
It works for $\textcolor{red}{f(x)=x}$ for all $x \in \mathbb{R}^{+}$.
This post has been edited 1 time. Last edited by Mathzeus1024, May 13, 2025, 10:01 AM
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rachelcassano
17 posts
#3 • 1 Y
Y by PikaPika999
Can you show working Mathzeus1024?
Z K Y
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jasperE3
11448 posts
#4
Y by
https://artofproblemsolving.com/community/c6h3564499p34775118
Z K Y
N Quick Reply
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a