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k a April Highlights and 2025 AoPS Online Class Information
jlacosta   0
Apr 2, 2025
Spring is in full swing and summer is right around the corner, what are your plans? At AoPS Online our schedule has new classes starting now through July, so be sure to keep your skills sharp and be prepared for the Fall school year! Check out the schedule of upcoming classes below.

WOOT early bird pricing is in effect, don’t miss out! If you took MathWOOT Level 2 last year, no worries, it is all new problems this year! Our Worldwide Online Olympiad Training program is for high school level competitors. AoPS designed these courses to help our top students get the deep focus they need to succeed in their specific competition goals. Check out the details at this link for all our WOOT programs in math, computer science, chemistry, and physics.

Looking for summer camps in math and language arts? Be sure to check out the video-based summer camps offered at the Virtual Campus that are 2- to 4-weeks in duration. 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 events:
[list][*]April 3rd (Webinar), 4pm PT/7:00pm ET, Learning with AoPS: Perspectives from a Parent, Math Camp Instructor, and University Professor
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April 9th (Webinar), 4:00pm PT/7:00pm ET, Learn about Video-based Summer Camps at the Virtual Campus
[*]April 10th (Math Jam), 4:30pm PT/7:30pm ET, 2025 MathILy and MathILy-Er Math Jam: Multibackwards Numbers
[*]April 22nd (Webinar), 4:00pm PT/7:00pm ET, Competitive Programming at AoPS (USACO).[/list]
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0 replies
jlacosta
Apr 2, 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
Problem with lcm
snowhite   3
N 33 minutes ago by ddot1
Prove that $\underset{n\to \infty }{\mathop{\lim }}\,\sqrt[n]{lcm(1,2,3,...,n)}=e$
Please help me! Thank you!
3 replies
snowhite
Yesterday at 5:19 AM
ddot1
33 minutes ago
Number Theory
fasttrust_12-mn   5
N 2 hours ago by GreekIdiot
Source: Pan African Mathematics Olympiad p6
Find all integers $n$ for which $n^7-41$ is the square of an integer
5 replies
fasttrust_12-mn
Aug 16, 2024
GreekIdiot
2 hours ago
Maximum number of nice subsets
FireBreathers   0
2 hours ago
Given a set $M$ of natural numbers with $n$ elements with $n$ odd number. A nonempty subset $S$ of $M$ is called $nice$ if the product of the elements of $S$ divisible by the sum of the elements of $M$, but not by its square. It is known that the set $M$ itself is good. Determine the maximum number of $nice$ subsets (including $M$ itself).
0 replies
1 viewing
FireBreathers
2 hours ago
0 replies
Floor double summation
CyclicISLscelesTrapezoid   52
N 2 hours ago by lpieleanu
Source: ISL 2021 A2
Which positive integers $n$ make the equation \[\sum_{i=1}^n \sum_{j=1}^n \left\lfloor \frac{ij}{n+1} \right\rfloor=\frac{n^2(n-1)}{4}\]true?
52 replies
CyclicISLscelesTrapezoid
Jul 12, 2022
lpieleanu
2 hours ago
Polynomial
Z_.   1
N 2 hours ago by rchokler
Let \( m \) be an integer greater than zero. Then, the value of the sum of the reciprocals of the cubes of the roots of the equation
\[
mx^4 + 8x^3 - 139x^2 - 18x + 9 = 0
\]is equal to:
1 reply
Z_.
3 hours ago
rchokler
2 hours ago
Existence of perfect squares
egxa   2
N 2 hours ago by pavel kozlov
Source: All Russian 2025 10.3
Find all natural numbers \(n\) for which there exists an even natural number \(a\) such that the number
\[
(a - 1)(a^2 - 1)\cdots(a^n - 1)
\]is a perfect square.
2 replies
egxa
Apr 18, 2025
pavel kozlov
2 hours ago
IMO 2014 Problem 4
ipaper   169
N 3 hours ago by YaoAOPS
Let $P$ and $Q$ be on segment $BC$ of an acute triangle $ABC$ such that $\angle PAB=\angle BCA$ and $\angle CAQ=\angle ABC$. Let $M$ and $N$ be the points on $AP$ and $AQ$, respectively, such that $P$ is the midpoint of $AM$ and $Q$ is the midpoint of $AN$. Prove that the intersection of $BM$ and $CN$ is on the circumference of triangle $ABC$.

Proposed by Giorgi Arabidze, Georgia.
169 replies
ipaper
Jul 9, 2014
YaoAOPS
3 hours ago
Inequalities
Scientist10   1
N 4 hours ago by Bergo1305
If $x, y, z \in \mathbb{R}$, then prove that the following inequality holds:
\[
\sum_{\text{cyc}} \sqrt{1 + \left(x\sqrt{1 + y^2} + y\sqrt{1 + x^2}\right)^2} \geq \sum_{\text{cyc}} xy + 2\sum_{\text{cyc}} x
\]
1 reply
Scientist10
6 hours ago
Bergo1305
4 hours ago
Tangents forms triangle with two times less area
NO_SQUARES   1
N 4 hours ago by Luis González
Source: Kvant 2025 no. 2 M2831
Let $DEF$ be triangle, inscribed in parabola. Tangents in points $D,E,F$ forms triangle $ABC$. Prove that $S_{DEF}=2S_{ABC}$. ($S_T$ is area of triangle $T$).
From F.S.Macaulay's book «Geometrical Conics», suggested by M. Panov
1 reply
NO_SQUARES
Yesterday at 9:08 AM
Luis González
4 hours ago
FE solution too simple?
Yiyj1   9
N 4 hours ago by jasperE3
Source: 101 Algebra Problems from the AMSP
Find all functions $f: \mathbb{R} \rightarrow \mathbb{R}$ such that the equality $$f(f(x)+y) = f(x^2-y)+4f(x)y$$holds for all pairs of real numbers $(x,y)$.

My solution

I feel like my solution is too simple. Is there something I did wrong or something I missed?
9 replies
Yiyj1
Apr 9, 2025
jasperE3
4 hours ago
interesting function equation (fe) in IR
skellyrah   2
N 4 hours ago by jasperE3
Source: mine
find all function F: IR->IR such that $$ xf(f(y)) + yf(f(x)) = f(xf(y)) + f(xy) $$
2 replies
skellyrah
Yesterday at 9:51 AM
jasperE3
4 hours ago
x^{2s}+x^{2s-1}+...+x+1 irreducible over $F_2$?
khanh20   2
N 5 hours ago by GreenKeeper
With $s\in \mathbb{Z}^+; s\ge 2$, whether or not the polynomial $P(x)=x^{2s}+x^{2s-1}+...+x+1$ irreducible over $F_2$?
2 replies
khanh20
Apr 21, 2025
GreenKeeper
5 hours ago
Equation over a finite field
loup blanc   2
N Yesterday at 6:16 PM by loup blanc
Find the set of $x\in\mathbb{F}_{5^5}$ such that the equation in the unknown $y\in \mathbb{F}_{5^5}$:
$x^3y+y^3+x=0$ admits $3$ roots: $a,a,b$ s.t. $a\not=b$.
2 replies
loup blanc
Tuesday at 6:08 PM
loup blanc
Yesterday at 6:16 PM
Can a 0-1 matrix square to the matrix with all ones?
Tintarn   4
N Yesterday at 5:47 PM by loup blanc
Source: IMC 2024, Problem 3
For which positive integers $n$ does there exist an $n \times n$ matrix $A$ whose entries are all in $\{0,1\}$, such that $A^2$ is the matrix of all ones?
4 replies
Tintarn
Aug 7, 2024
loup blanc
Yesterday at 5:47 PM
Integration Marathon
WireCat   252
N Feb 13, 2017 by j___d
This is an integral marathon! Standard marathon rules, hide problems and solutions. I would appreciate it if you would add hint(s) to the problem as to help "guide" the reader to the correct solution (as I currently suck at integrating... rip). The first problem will be easy, and each problem after it will increase in difficulty minimally.
Remember: If you forget the +C term, you're going to have a bad time.
Now: P1
Hint
252 replies
WireCat
Jul 23, 2016
j___d
Feb 13, 2017
Integration Marathon
G H J
G H BBookmark kLocked kLocked NReply
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WireCat
365 posts
#1 • 4 Y
Y by TJK7, ahmedosama, Adventure10, Mango247
This is an integral marathon! Standard marathon rules, hide problems and solutions. I would appreciate it if you would add hint(s) to the problem as to help "guide" the reader to the correct solution (as I currently suck at integrating... rip). The first problem will be easy, and each problem after it will increase in difficulty minimally.
Remember: If you forget the +C term, you're going to have a bad time.
Now: P1
Hint
This post has been edited 4 times. Last edited by WireCat, Aug 3, 2016, 2:15 PM
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hinna
974 posts
#2 • 1 Y
Y by Adventure10
(Mandatory undertale reference aside), I think this is supposed to go into college math.
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Darkdoger
216 posts
#3 • 2 Y
Y by Adventure10, Mango247
Do you feel your sins crawling on your back?
(Undertale)
And yes I believe all calculus is required to go to college math.
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WireCat
365 posts
#4 • 1 Y
Y by Adventure10
hinna wrote:
(Mandatory undertale reference aside), I think this is supposed to go into college math.

I'm pretty sure undertale has "You have a feeling that you're going to have a bad time", this is actually a reference to SP.
This post has been edited 1 time. Last edited by WireCat, Jul 24, 2016, 12:54 AM
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Darkdoger
216 posts
#5 • 1 Y
Y by Adventure10
S1
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WireCat
365 posts
#6 • 2 Y
Y by Adventure10, Mango247
@above, if you could post a problem, that would be great :-D
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Darkdoger
216 posts
#7 • 2 Y
Y by Adventure10, Mango247
Well, can I put a problem then can someone else latex it up to make it readable?
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WireCat
365 posts
#8 • 2 Y
Y by Adventure10, Mango247
Sure, although I think that learning LaTeX would be worth it :-D
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Darkdoger
216 posts
#9 • 3 Y
Y by ahmedosama, Adventure10, Mango247
Yeah, I'm trying but I don't really want to memorize all of the symbols, just essential ones.

P2
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WireCat
365 posts
#10 • 2 Y
Y by Adventure10, Mango247
P2
S2
P3
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AnderExtrema
417 posts
#11 • 3 Y
Y by rafayaashary1, Adventure10, Mango247
Memorizing? Just like theorems, it isn't something you memorize. It's something you do enough such that you remember it. They are also very intuitive.
As for the re-write in LaTeX.

S1

And it seems Wire Cat has already re-written P2.
This post has been edited 2 times. Last edited by AnderExtrema, Jul 24, 2016, 1:34 AM
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Darkdoger
216 posts
#12 • 1 Y
Y by Adventure10
/request move to college math.
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hinna
974 posts
#13 • 1 Y
Y by Adventure10
WireCat wrote:
P2
S2
P3

For P3, if the radius of the circle is $r$, then the diameter is $2r$ so the sides are each $2r$ and looking for perimeter, we get $8r$. Is it this simple or am I missing something? But the anti derivative becomes Answer

As I am not taking calculus or precalc, I have no idea if this is too hard or not. If it is, you can skip it:p4
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Darkdoger
216 posts
#14 • 2 Y
Y by Adventure10, Mango247
That one will work just fine.
S4
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Kingofmath101
2210 posts
#15 • 3 Y
Y by ahmedosama, Adventure10, Mango247
P5
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a