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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:
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[*]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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0 replies
jlacosta
May 1, 2025
0 replies
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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
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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
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Challenge: Make every number to 100 using 4 fours
CJB19   227
N 18 minutes ago by complex0
I've seen this attempted a lot but I want to see if the AoPS community can actually do it. Using ONLY 4 fours and math operations, make as many numbers as you can. Try to go in order. I'll start:
$$(4-4)*4*4=0$$$$4-4+4/4=1$$$$4/4+4/4=2$$$$(4+4+4)/4=3$$$$4+(4-4)*4=4$$$$4+4^{4-4}=5$$$$4!/4+4-4=6$$$$4+4-4/4=7$$$$4+4+4-4=8$$
227 replies
CJB19
May 15, 2025
complex0
18 minutes ago
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FE with conditions on $x,y$
Adywastaken   2
N 34 minutes ago by Adywastaken
Source: OAO
Find all functions $f:\mathbb{R_{+}}\rightarrow \mathbb{R_{+}}$ such that $\forall y>x>0$,
\[ f(x^2+f(y))=f(xf(x))+y \]
2 replies
Adywastaken
Yesterday at 6:18 PM
Adywastaken
34 minutes ago
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The daily problem!
Leeoz   195
N 42 minutes ago by complex0
Every day, I will try to post a new problem for you all to solve! If you want to post a daily problem, you can! :)

Please hide solutions and answers, hints are fine though! :)

Problems usually get harder throughout the week, so Sunday is the easiest and Saturday is the hardest!

Past Problems!
195 replies
Leeoz
Mar 21, 2025
complex0
42 minutes ago
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2021 EGMO P4: Reflection of A over EF lies on BC
anser   48
N an hour ago by cursed_tangent1434
Source: EGMO 2021 P4
Let $ABC$ be a triangle with incenter $I$ and let $D$ be an arbitrary point on the side $BC$. Let the line through $D$ perpendicular to $BI$ intersect $CI$ at $E$. Let the line through $D$ perpendicular to $CI$ intersect $BI$ at $F$. Prove that the reflection of $A$ across the line $EF$ lies on the line $BC$.
48 replies
anser
Apr 13, 2021
cursed_tangent1434
an hour ago
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Serbian selection contest for the IMO 2025 - P2
OgnjenTesic   10
N 2 hours ago by Mahdi_Mashayekhi
Source: Serbian selection contest for the IMO 2025
Let $ABC$ be an acute triangle. Let $A'$ be the reflection of point $A$ over the line $BC$. Let $O$ and $H$ be the circumcenter and the orthocenter of triangle $ABC$, respectively, and let $E$ be the midpoint of segment $OH$. Let $D$ and $L$ be the points where the reflection of line $AA'$ with respect to line $OA'$ intersects the circumcircle of triangle $ABC$, where point $D$ lies on the arc $BC$ not containing $A$. If \( M \) is a point on the line \( BC \) such that \( OM \perp AD \), prove that \( \angle MAD = \angle EAL \).

Proposed by Strahinja Gvozdić
10 replies
OgnjenTesic
Thursday at 4:02 PM
Mahdi_Mashayekhi
2 hours ago
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find all Polynomials
andria   9
N 2 hours ago by A.H.H
Source: Iranian third round 2015 algebra problem 5
Find all polynomials $p(x)\in\mathbb{R}[x]$ such that for all $x\in \mathbb{R}$:
$p(5x)^2-3=p(5x^2+1)$ such that:
$a) p(0)\neq 0$
$b) p(0)=0$
9 replies
andria
Sep 8, 2015
A.H.H
2 hours ago
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AT // BC wanted
parmenides51   105
N 2 hours ago by Adywastaken
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)
105 replies
parmenides51
Sep 22, 2020
Adywastaken
2 hours ago
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Two lines concur on (ABC)
amar_04   19
N 2 hours ago by Giant_PT
Source: XVII Sharygin Corespondnce Round P13
In triangle $ABC$ with circumcircle $\Omega$ and incenter $I$, point $M$ bisects arc $BAC$ and line $\overline{AI}$ meets $\Omega$ at $N\ne A$. The excircle opposite to $A$ touches $\overline{BC}$ at point $E$. Point $Q\ne I$ on the circumcircle of $\triangle MIN$ is such that $\overline{QI}\parallel\overline{BC}$. Prove that the lines $\overline{AE}$ and $\overline{QN}$ meet on $\Omega$.
19 replies
amar_04
Mar 2, 2021
Giant_PT
2 hours ago
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9 How many squares do you have memorized
LXC007   94
N 2 hours ago by ohiorizzler1434
How many squares have you memorized. I have 1-20

Edit: to clarify i mean positive squares from 1 so if you say ten you mean you memorized the squares 1,2,3,4,5,6,7,8,9 and 10
94 replies
LXC007
May 17, 2025
ohiorizzler1434
2 hours ago
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Nice problem of concurrency
deraxenrovalo   0
2 hours ago
Let $(I)$ be an inscribed circle of $\triangle$$ABC$ and touching $BC$, $CA$, $AB$ at $D$, $E$, $F$ respectively. Let $EE'$ and $FF'$ be diameters of $(I)$. Let $X$ and $Y$ be the pole of $DE'$ and $DF'$ with respect to $(I)$, respectively. $BE$ cuts $(I)$ again at $K$. $CF$ cuts $(I)$ again at $L$. The tangent at $K$ of $(I)$ cuts $AX$ at $M$. The tangent at $L$ of $(I)$ cuts $AY$ at $N$. Let $U$ and $V$ be midpoint of $IM$ and $IN$, respectively.

Show that : $UV$, $E'F'$ and perpendicular bisector of $ID$ are concurrent.
0 replies
deraxenrovalo
2 hours ago
0 replies
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A hunter and an invisible rabbit are playing again...
Phorphyrion   1
N 2 hours ago by JARP091
Source: 2021 Discord CCCC P4
A hunter and an invisible rabbit play a game in a $2021\times 2021$ grid. The rabbit's starting square is $P_0$ (unknown to the hunter), and after $n-1$ rounds, the rabbit is at square $P_{n-1}$. In the $n$-th round of the game, two things occur in order:

(i) The rabbit moves invisibly to a square $P_n$ which shares a point with $P_{n-1}$ (There are up to eight of these).

(ii) A tracking device searches $k$ squares of the hunter's choosing. If the rabbit is in one of these squares, the rabbit is captured and the game ends.

For what $k$ can the rabbit avoid capture indefinitely?
1 reply
Phorphyrion
Dec 24, 2023
JARP091
2 hours ago
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SL 2015 G1: Prove that IJ=AH
Problem_Penetrator   137
N 3 hours ago by heheman
Source: IMO 2015 Shortlist, G1
Let $ABC$ be an acute triangle with orthocenter $H$. Let $G$ be the point such that the quadrilateral $ABGH$ is a parallelogram. Let $I$ be the point on the line $GH$ such that $AC$ bisects $HI$. Suppose that the line $AC$ intersects the circumcircle of the triangle $GCI$ at $C$ and $J$. Prove that $IJ = AH$.
137 replies
Problem_Penetrator
Jul 7, 2016
heheman
3 hours ago
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IMO Shortlist 2011, G2
WakeUp   30
N 3 hours ago by ezpotd
Source: IMO Shortlist 2011, G2
Let $A_1A_2A_3A_4$ be a non-cyclic quadrilateral. Let $O_1$ and $r_1$ be the circumcentre and the circumradius of the triangle $A_2A_3A_4$. Define $O_2,O_3,O_4$ and $r_2,r_3,r_4$ in a similar way. Prove that
\[\frac{1}{O_1A_1^2-r_1^2}+\frac{1}{O_2A_2^2-r_2^2}+\frac{1}{O_3A_3^2-r_3^2}+\frac{1}{O_4A_4^2-r_4^2}=0.\]

Proposed by Alexey Gladkich, Israel
30 replies
WakeUp
Jul 13, 2012
ezpotd
3 hours ago
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Competitions
CJB19   4
N 4 hours ago by Spacepandamath13
So, I'm a little bit silly and I didn't even know about the AMC 8 until this year, so I'm curious now. What are the other MSM level competitions? I only really know about AMC 8 & 10, Mathcounts, and AIME.
4 replies
CJB19
Yesterday at 4:02 PM
Spacepandamath13
4 hours ago
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J
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An algebra math problem
AVY2024   6
N Apr 18, 2025 by Roger.Moore
Solve for a,b
ax-2b=5bx-3a
6 replies
AVY2024
Apr 8, 2025
Roger.Moore
Apr 18, 2025
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An algebra math problem
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Reveal topic tags
algebra
nmtc
equation
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AVY2024
29 posts
AVY2024
#1 h  Apr 8, 2025, 10:55 AM
Y by
Solve for a,b
ax-2b=5bx-3a
Z K Y
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Inaaya
413 posts
Inaaya
#2 h  Apr 8, 2025, 1:40 PM • 1 Y
Y by Exponent11
There are 3 variables and one equation, this thing can theoretically have infinite solution sets
Z K Y
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sp0rtman00000
2 posts
sp0rtman00000
#3 h  Apr 11, 2025, 11:03 AM
Y by
On the R or on the N?
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Pengu14
634 posts
Pengu14
#5 h  Apr 11, 2025, 3:24 PM
Y by
Inaaya wrote:
There are 3 variables and one equation, this thing can theoretically have infinite solution sets

I believe they’re looking for a and b such that the equation holds for ALL x.
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Pengu14
634 posts
Pengu14
#6 h  Apr 11, 2025, 3:25 PM
Y by
AVY2024 wrote:
Solve for a,b
ax-2b=5bx-3a

We have a=5b and 3a=2b. The only solution is a=b=0.
Z K Y
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Runner1600
12 posts
Runner1600
#7 h  Apr 11, 2025, 3:56 PM
Y by
Pengu14 wrote:
AVY2024 wrote:
Solve for a,b
ax-2b=5bx-3a

We have a=5b and 3a=2b. The only solution is a=b=0.

That is what I got
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Roger.Moore
5 posts
Roger.Moore
#8 h  Apr 18, 2025, 6:03 PM
Y by
The x there are parameter?
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