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k a August Highlights and 2025 AoPS Online Class Information
jwelsh   0
Yesterday at 2:14 PM
CONGRATULATIONS to all the competitors at this year’s International Mathematical Olympiad (IMO)! The US Team took second place with 5 gold medals and 1 silver - we are proud to say that each member of the 2025 IMO team has participated in an AoPS WOOT (Worldwide Online Olympiad Training) class!

"As a parent, I'm deeply grateful to AoPS. Tiger has taken very few math courses outside of AoPS, except for a local Math Circle that doesn't focus on Olympiad math. AoPS has been one of the most important resources in his journey. Without AoPS, Tiger wouldn't be where he is today — especially considering he's grown up in a family with no STEM background at all."
— Doreen Dai, parent of IMO US Team Member Tiger Zhang

Interested to learn more about our WOOT programs? Check out the course page here or join a Free Scheduled Info Session. Early bird pricing ends August 19th!:
CodeWOOT Code Jam - Monday, August 11th
ChemWOOT Chemistry Jam - Wednesday, August 13th
PhysicsWOOT Physics Jam - Thursday, August 14th
MathWOOT Math Jam - Friday, August 15th

There is still time to enroll in our last wave of summer camps that start in August at the Virtual Campus, our video-based platform, for math and language arts! From Math Beasts Camp 6 (Prealgebra Prep) to AMC 10/12 Prep, you can find an informative 2-week camp before school starts. Plus, our math camps don’t have homework and cover cool enrichment topics like graph theory. Our language arts courses will build the foundation for next year’s challenges, such as Language Arts Triathlon for levels 5-6 and Academic Essay Writing for high school students.

Lastly, Fall is right around the corner! 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. We’ve opened new Academy locations in San Mateo, CA, Pasadena, CA, Saratoga, CA, Johns Creek, GA, Northbrook, IL, and Upper West Side (NYC), New York.

Our full course list for upcoming classes is below:
All classes run 7:30pm-8:45pm ET/4:30pm - 5:45pm PT unless otherwise noted.
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0 replies
jwelsh
Yesterday at 2:14 PM
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
Circle problem
littleduckysteve   2
N 3 minutes ago by vanstraelen
3 circles are drawn such that they are externally tangent to each other. The circles have radius, 1,2, and 3 respectively. A bigger circle is drawn such that all three circles are internally tangent to it. If we call the center of the bigger circle, $A$, and the centroid of the triangle formed by the centers of the three smaller circles, B. What is the length $AB^2$.
2 replies
littleduckysteve
Yesterday at 2:33 PM
vanstraelen
3 minutes ago
9 AMC 10A vs. AMC 10B
a.zvezda   0
20 minutes ago
Usually, I think AMC 10B is harder but, it depends. Also, what are your 2024 AMC 10 scores?
0 replies
a.zvezda
20 minutes ago
0 replies
Equal segments with humpty and dumpty points.
Kratsneb   1
N 23 minutes ago by aqwxderf
Let $X$, $Y$ be such points on sides $AB$, $AC$ of a triangle $ABC$ that $BXYC$ is cyclic. $BY \cap CX = D$, $N$ is the midpoint of $AD$. In triangles $BDX$ and $CDY$ let $P$, $Q$ be the $D$-humpty points and let $S$, $T$ be the $D$-dumpty points. Prove that $AP = AQ$ and $NS = NT$.
IMAGE
1 reply
Kratsneb
4 hours ago
aqwxderf
23 minutes ago
Multivariate polynomial must vanish on all permutations
DottedCaculator   2
N 24 minutes ago by CANBANKAN
Source: 2025 ELMO Shortlist A4
Fix positive integers $n$ and $k$ with $n \geq k$. Determine the smallest positive integer $d$ satisfying the following condition:

For any (not necessarily distinct) real numbers $a_1$, $\dots$, $a_n$, there exists a real-coefficient polynomial $f$ in $k$ variables satisfying the following properties:
[list]
[*] $f$ has degree at most $d$;
[*] $f$ is not identically $0$;
[*] for any permutation $b_1, \ldots, b_n$ of $a_1, \ldots, a_n$, the equation $f(b_1, \ldots, b_k) = 0$ holds.
[/list]

Benny Wang
2 replies
DottedCaculator
Jun 30, 2025
CANBANKAN
24 minutes ago
Find the largest value of p
Darealzolt   8
N 30 minutes ago by P0tat0b0y
It is known that
\[
\sqrt{x-3}+\sqrt{6-x} \leq p
\]In which \(x \in \mathbb{R}\), hence find the largest value of \(p\).
8 replies
Darealzolt
Jun 6, 2025
P0tat0b0y
30 minutes ago
Circle geometry proof
littleduckysteve   1
N an hour ago by littleduckysteve
Suppose 3 circles are drawn in the 2-dimensional grid such that no two circles are of the same radius. Now we draw the 2 lines which are both tangent to the smallest circle and the median circle, and call their intersection, A. Now we do the same thing for the biggest circle and the smallest, and finally the biggest and the median circles. Now assume that we call these two points, B and C. Prove that A, B, and C are all colinear regardless of where the circles are.
1 reply
littleduckysteve
Today at 7:29 AM
littleduckysteve
an hour ago
Combinatorics
slimshady360   0
an hour ago
Source: IMO 2005-Problem 6.
Does anybody have any idea how to solve this with graph theory?
0 replies
slimshady360
an hour ago
0 replies
USAMO 2003 Problem 1
MithsApprentice   75
N an hour ago by SomeonecoolLovesMaths
Prove that for every positive integer $n$ there exists an $n$-digit number divisible by $5^n$ all of whose digits are odd.
75 replies
MithsApprentice
Sep 27, 2005
SomeonecoolLovesMaths
an hour ago
Some of my less-seen proposals
navid   7
N an hour ago by shaboon
Dear friends,

Since 2003, I have had several nice days in AOPS-- i.e., Mathlinks; as some of you may remember. I decided to share you some of my less-seen proposals. Some of them may be considered as some early ethudes; several of them already appeared on some competitions or journals. I hope you like them and this be a good starting point for working on them. Please take a look at the following link.

https://drive.google.com/file/d/1bntcjZAHZ-WN1lfGbNbz0uyFvhBTMEhz/view?usp=sharing

Best regards,
Navid.
7 replies
navid
Jul 30, 2025
shaboon
an hour ago
Ugly functional equation
Taha1381   11
N an hour ago by shaboon
Source: Iranian third round 2019 Finals algebra exam problem 3
Let $a,b,c$ be non-zero distinct real numbers so that there exist functions $f,g:\mathbb{R}^{+} \to \mathbb{R}$ so that:

$af(xy)+bf(\frac{x}{y})=cf(x)+g(y)$

For all positive real $x$ and large enough $y$.

Prove that there exists a function $h:\mathbb{R}^{+} \to \mathbb{R}$ so that:

$f(xy)+f(\frac{x}{y})=2f(x)+h(y)$

For all positive real $x$ and large enough $y$.
11 replies
Taha1381
Aug 18, 2019
shaboon
an hour ago
Bicentric Quadrilateral Concurrence
anantmudgal09   2
N 2 hours ago by MathLuis
Source: India-Iran-Singapore-Taiwan Friendly Contest 2025 Problem 2
Let $ABCD$ be a quadrilateral with both an incircle and a circumcircle. Let $I$ and $O$ be the incenter and circumcenter of $ABCD$, respectively. Let $E$ be the intersection of lines $AB$ and $CD$, and let $F$ be the intersection of lines $BC$ and $DA$. Let $X$ and $Y$ be the intersections of the line $FI$ with lines $AB$ and $CD$, respectively. Prove that the circumcircle of $\triangle EIF$, the circumcircle of $\triangle EXY$, and the line $FO$ are concurrent.
2 replies
anantmudgal09
Today at 7:15 AM
MathLuis
2 hours ago
find all continuous functions
aktyw19   3
N 2 hours ago by jasperE3
Find all continuous functions $f:\mathbb{R}\to\mathbb{R}$ such that $f(xy)+f(x+y)=f(xy+x)+f(y)$.
3 replies
aktyw19
Sep 28, 2013
jasperE3
2 hours ago
Find all functions
aktyw19   2
N 2 hours ago by jasperE3
Find all functions $f:\mathbb{R}\rightarrow\mathbb{R}$ such that
$f(x^2+y^2)=f(f(x))+f(xy)+f(f(y))$ $\forall x, y\in\mathbb{R}$
2 replies
aktyw19
Mar 27, 2014
jasperE3
2 hours ago
intersting problem
teomihai   2
N 2 hours ago by teomihai
Prove $\frac{1}{5n+1}+\frac{1}{5n+2}+...+\frac{1}{10n}>\frac{3}{5} $ for any $n>0$,integer .
2 replies
teomihai
2 hours ago
teomihai
2 hours ago
Challenging Optimization Problem
Shiyul   5
N Apr 22, 2025 by exoticc
Let $xyz = 1$. Find the minimum and maximum values of $\frac{1}{1 + x + xy}$ + $\frac{1}{1 + y + yz}$ + $\frac{1}{1 + z + zx}$

Can anyone give me a hint? I got that either the minimum or maximum was 1, but I'm sure if I'm correct.
5 replies
Shiyul
Apr 21, 2025
exoticc
Apr 22, 2025
Challenging Optimization Problem
G H J
G H BBookmark kLocked kLocked NReply
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Shiyul
22 posts
#1
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Let $xyz = 1$. Find the minimum and maximum values of $\frac{1}{1 + x + xy}$ + $\frac{1}{1 + y + yz}$ + $\frac{1}{1 + z + zx}$

Can anyone give me a hint? I got that either the minimum or maximum was 1, but I'm sure if I'm correct.
This post has been edited 2 times. Last edited by Shiyul, Apr 21, 2025, 8:23 PM
Reason: latex problem
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SPQ
5 posts
#2
Y by
Hi! You're absolutely right—the minimum and maximum are both 1.

Here’s a little hint that might help clarify things:

The expression 1 + x + xy can be rewritten as:
1 + x(1 + y) = 1 + xyz(1 + y)/yz.
Since xyz = 1, this simplifies to:
1 + x + xy = 1 + (1 + y)/yz = (1 + y + yz)/yz.

In a similar way, you can show that:
1 + y + yz = (1 + z + zx)/zx.

Hope that helps.
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aidan0626
2113 posts
#3
Y by
try plugging in $z=\frac{1}{xy}$ into the expression, you might notice things simplify quite nicely :)
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lbh_qys
682 posts
#4
Y by
Try let $x =\frac ba$.
Z K Y
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vanstraelen
9190 posts
#5
Y by
$P(x,y,z)=\frac{1}{1 + x + xy}+\frac{1}{1 + y + yz}+\frac{1}{1 + z + zx}=1$, there is no maximum/minimum.
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exoticc
9 posts
#6
Y by
The value of the expression is 1
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