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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
[*]April 8th (Math Jam), 4:30pm PT/7:30pm ET, 2025 MATHCOUNTS State Discussion
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
Diophantine equation !
ComplexPhi   9
N 10 minutes ago by MATHS_ENTUSIAST
Determine all triples $(m , n , p)$ satisfying :
\[n^{2p}=m^2+n^2+p+1\]
where $m$ and $n$ are integers and $p$ is a prime number.
9 replies
ComplexPhi
Feb 4, 2015
MATHS_ENTUSIAST
10 minutes ago
Cool inequality
giangtruong13   1
N 19 minutes ago by grupyorum
Source: Hanoi Specialized School’s Practical Math Entrance Exam (Round 2)
Let $a,b,c$ be real positive numbers such that: $a^2+b^2+c^2=4abc-1$. Prove that: $$a+b+c \geq \sqrt{abc}+2$$
1 reply
giangtruong13
an hour ago
grupyorum
19 minutes ago
Primes and sets
mathisreaI   39
N 20 minutes ago by awesomehuman
Source: IMO 2022 Problem 3
Let $k$ be a positive integer and let $S$ be a finite set of odd prime numbers. Prove that there is at most one way (up to rotation and reflection) to place the elements of $S$ around the circle such that the product of any two neighbors is of the form $x^2+x+k$ for some positive integer $x$.
39 replies
mathisreaI
Jul 13, 2022
awesomehuman
20 minutes ago
Interesting number theory
giangtruong13   1
N 21 minutes ago by grupyorum
Source: Hanoi Specialized School’s Practical Math Entrance Exam (Round 2)
Let $a,b$ be integer numbers $\geq 3$ satisfy that:$a^2=b^3+ab$. Prove that:
a) $a,b$ are even
b) $4b+1$ is a perfect square number
c) $a$ can’t be any power $\geq 1$ of a positive integer number
1 reply
giangtruong13
an hour ago
grupyorum
21 minutes ago
function
CarlFriedrichGauss-1777   4
N 25 minutes ago by jasperE3
Find all functions $f: \mathbb{R}^{+} \rightarrow \mathbb{R}^{+}$ such that:
$f(2021+xf(y))=yf(x+y+2021)$
4 replies
CarlFriedrichGauss-1777
Jun 4, 2021
jasperE3
25 minutes ago
Find all functions f with f(x+y)+f(x)f(y)=f(xy)+(y+1)f(x)+(x+1)f(y)
Martin N.   10
N 43 minutes ago by jasperE3
Source: (4th Middle European Mathematical Olympiad, Individual Competition, Problem 1)
Find all functions $f:\mathbb{R}\to\mathbb{R}$ such that for all $x, y\in\mathbb{R}$, we have
\[f(x+y)+f(x)f(y)=f(xy)+(y+1)f(x)+(x+1)f(y).\]
10 replies
Martin N.
Sep 11, 2010
jasperE3
43 minutes ago
k interesting fe
skellyrah   1
N an hour ago by jasperE3
find all functions $f :\mathbb{R} \to \mathbb{R}$ such that $$xf(x+yf(xy)) + f(f(x)) = f(xf(y))^2 + (x+1)f(x)$$
1 reply
skellyrah
an hour ago
jasperE3
an hour ago
International FE olympiad P3
Functional_equation   22
N an hour ago by jasperE3
Source: IFEO Day 1 P3
Find all functions $f:\mathbb R^+\rightarrow \mathbb R^+$ such that$$f(f(x)f(f(x))+y)=xf(x)+f(y)$$for all $x,y\in \mathbb R^+$

$\textit{Proposed by Functional\_equation, Mr.C and TLP.39}$
22 replies
Functional_equation
Feb 6, 2021
jasperE3
an hour ago
Arbitrary point on BC and its relation with orthocenter
falantrng   19
N an hour ago by jrpartty
Source: Balkan MO 2025 P2
In an acute-angled triangle \(ABC\), \(H\) be the orthocenter of it and \(D\) be any point on the side \(BC\). The points \(E, F\) are on the segments \(AB, AC\), respectively, such that the points \(A, B, D, F\) and \(A, C, D, E\) are cyclic. The segments \(BF\) and \(CE\) intersect at \(P.\) \(L\) is a point on \(HA\) such that \(LC\) is tangent to the circumcircle of triangle \(PBC\) at \(C.\) \(BH\) and \(CP\) intersect at \(X\). Prove that the points \(D, X, \) and \(L\) lie on the same line.

Proposed by Theoklitos Parayiou, Cyprus
19 replies
falantrng
Yesterday at 11:47 AM
jrpartty
an hour ago
Interesting inequality
sqing   3
N an hour ago by angelazhang.zlh
Source: Own
Let $ a,b,c>0  . $ Prove that
$$\frac{a}{b}+ \frac{kb^2}{c^2} + \frac{c}{a}\geq 5\sqrt[5]{\frac{k}{16}}$$Where $ k >0. $
$$\frac{a}{b}+ \frac{16b^2}{c^2} + \frac{c}{a}\geq 5$$$$\frac{a}{b}+ \frac{ b^2}{2c^2} + \frac{c}{a}\geq \frac{5}{2} $$
3 replies
sqing
4 hours ago
angelazhang.zlh
an hour ago
hard problem
Cobedangiu   10
N an hour ago by Cobedangiu
Let $a,b,c>0$ and $a+b+c=3$. Prove that:
$\dfrac{4}{a+b}+\dfrac{4}{b+c}+\dfrac{4}{c+a} \le \dfrac{1}{a}+\dfrac{1}{b}+\dfrac{1}{c}+3$
10 replies
Cobedangiu
Apr 21, 2025
Cobedangiu
an hour ago
inequalities
Cobedangiu   0
an hour ago
Source: UCT
Let $a,b,c>0$ and $a+b+c=3$ Prove that:
$\sum \dfrac{\sqrt{a^2+a+1}}{2a^2+10a+9}\ge \dfrac{\sqrt{3}}{7}$
0 replies
Cobedangiu
an hour ago
0 replies
AT // BC wanted
parmenides51   103
N an hour ago by reni_wee
Source: IMO 2019 SL G1
Let $ABC$ be a triangle. Circle $\Gamma$ passes through $A$, meets segments $AB$ and $AC$ again at points $D$ and $E$ respectively, and intersects segment $BC$ at $F$ and $G$ such that $F$ lies between $B$ and $G$. The tangent to circle $BDF$ at $F$ and the tangent to circle $CEG$ at $G$ meet at point $T$. Suppose that points $A$ and $T$ are distinct. Prove that line $AT$ is parallel to $BC$.

(Nigeria)
103 replies
parmenides51
Sep 22, 2020
reni_wee
an hour ago
f(f(x)+y) = x+f(f(y))
NicoN9   4
N an hour ago by Tony_stark0094
Source: own, well this is my first problem I've ever write
Find all functions $f: \mathbb{R} \rightarrow \mathbb{R}$ such that\[
f(f(x)+y) = x+f(f(y))
\]for all $x, y\in \mathbb{R}$.
4 replies
NicoN9
Today at 10:03 AM
Tony_stark0094
an hour ago
3-dimensional cross (quicky)
Peter   3
N Sep 27, 2005 by Peter
Source: flanders '88/2
A 3-dimensional cross is made up of 7 cubes, one central cube and 6 cubes that share a face with it.
The cross is inscribed in a circle with radius 1. What's its volume?
3 replies
Peter
Sep 27, 2005
Peter
Sep 27, 2005
3-dimensional cross (quicky)
G H J
G H BBookmark kLocked kLocked NReply
Source: flanders '88/2
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Peter
3615 posts
#1 • 2 Y
Y by Adventure10, Mango247
A 3-dimensional cross is made up of 7 cubes, one central cube and 6 cubes that share a face with it.
The cross is inscribed in a circle with radius 1. What's its volume?
Z K Y
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fourierseries
291 posts
#2 • 2 Y
Y by Adventure10, Mango247
If we denote the side by $s$, then we get the relation

$(\frac{s}{2})^2+(\frac{s}{2})^2+(\frac{3s}{2})^2=1$. Solve for s.
Z K Y
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fourierseries
291 posts
#3 • 2 Y
Y by Adventure10, Mango247
Sorry, I think I hit submit too quickly.

Therefore $s=\frac{2}{\sqrt(11)}$,

and $V=7s^3=\frac{56}{11\sqrt{11}}$
Z K Y
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Peter
3615 posts
#4 • 2 Y
Y by Adventure10, Mango247
Indeed. :)
Z K Y
N Quick Reply
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