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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:
[list][*]May 9th, 4:30pm PT/7:30pm ET, Casework 2: Overwhelming Evidence — A Text Adventure, a game where participants will work together to navigate the map, solve puzzles, and win! All are welcome.
[*]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
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
Assam Mathematics Olympiad 2022 Category III Q17
SomeonecoolLovesMaths   1
N 2 minutes ago by nyacide
Consider a rectangular grid of points consisting of $4$ rows and $84$ columns. Each point is coloured with one of the colours red, blue or green. Show that no matter whatever way the colouring is done, there always exist four points
of the same colour that form the vertices of a rectangle. An illustration is shown in the figure below.
1 reply
SomeonecoolLovesMaths
Sep 12, 2024
nyacide
2 minutes ago
Inequalities
sqing   6
N 24 minutes ago by DAVROS
Let $a,b,c >1 $ and $ \frac{1}{a-1}+\frac{1}{b-1}+\frac{1}{c-1}=1.$ Show that$$ab+bc+ca \geq 48$$$$\frac{1}{a}+\frac{1}{b}+\frac{1}{c}\leq \frac{3}{4}$$Let $a,b,c >1 $ and $ \frac{1}{a-1}+\frac{1}{b-1}+\frac{1}{c-1}=2.$ Show that$$ab+bc+ca \geq \frac{75}{4}$$$$\frac{1}{a}+\frac{1}{b}+\frac{1}{c}\leq \frac{6}{5}$$Let $a,b,c >1 $ and $ \frac{1}{a-1}+\frac{1}{b-1}+\frac{1}{c-1}=3.$ Show that$$ab+bc+ca \geq 12$$$$\frac{1}{a}+\frac{1}{b}+\frac{1}{c}\leq \frac{3}{2}$$
6 replies
sqing
Yesterday at 9:04 AM
DAVROS
24 minutes ago
Assam Mathematics Olympiad 2022 Category III Q14
SomeonecoolLovesMaths   1
N 32 minutes ago by nyacide
The following sum of three four digits numbers is divisible by $75$, $7a71 + 73b7 + c232$, where $a, b, c$ are decimal digits. Find the necessary conditions in $a, b, c$.
1 reply
SomeonecoolLovesMaths
Sep 12, 2024
nyacide
32 minutes ago
Number theory
EeEeRUT   0
38 minutes ago
Source: Thailand MO 2025 P10
Let $n$ be a positive integer. Show that there exist a polynomial $P(x)$ with integer coefficient that satisfy the following
[list]
[*]Degree of $P(x)$ is at most $2^n - n -1$
[*]$|P(k)| = (k-1)!(2^n-k)!$ for each $k \in \{1,2,3,\dots,2^n\}$
[/list]
0 replies
EeEeRUT
38 minutes ago
0 replies
help me please,thanks
tnhan.129   1
N 40 minutes ago by pco
find f: R+ -> R such that:
f(x)/x + f(y)/y = (1/x + 1/y).f(sqrt(xy))
1 reply
tnhan.129
May 11, 2025
pco
40 minutes ago
What is thiss
EeEeRUT   0
41 minutes ago
Source: Thailand MO 2025 P6
Find all function $f: \mathbb{R}^+ \rightarrow \mathbb{R}$,such that the inequality $$f(x) + f(\frac{y}{x}) \leqslant \frac{x^3}{y^2} + \frac{y}{x^3}$$holds for all positive reals $x,y$ and for every positive real $x$, there exist positive reals $y$, such that the equality holds.
0 replies
EeEeRUT
41 minutes ago
0 replies
Divisibility with the polynomial ax^{75}+b
MathMystic33   1
N 43 minutes ago by RagvaloD
Source: Macedonian Mathematical Olympiad 2025 Problem 4
Let $P(x)=a x^{75}+b$ be a polynomial where \(a\) and \(b\) are coprime integers in the set \(\{1,2,\dots,151\}\), and suppose it satisfies the following condition: there exists at most one prime \(p\) such that for every positive integer \(k\), \(p\mid P(k)\). Prove that for every prime \(q \neq p\) there exists a positive integer \(k\) for which $q^2 \mid P(k).$
1 reply
MathMystic33
Yesterday at 5:50 PM
RagvaloD
43 minutes ago
inequality
xytunghoanh   4
N an hour ago by lbh_qys
For $a,b,c\ge 0$. Let $a+b+c=3$.
Prove or disprove
\[\sum ab +\sum ab^2 \le 6\]
4 replies
xytunghoanh
3 hours ago
lbh_qys
an hour ago
BMO Shortlist 2021 G1
Lukaluce   10
N an hour ago by s27_SaparbekovUmar
Source: BMO Shortlist 2021
Let $ABC$ be a triangle with $AB < AC < BC$. On the side $BC$ we consider points $D$
and $E$ such that $BA = BD$ and $CE = CA$. Let $K$ be the circumcenter of triangle $ADE$ and
let $F$, $G$ be the points of intersection of the lines $AD$, $KC$ and $AE$, $KB$ respectively. Let $\omega_1$ be
the circumcircle of triangle $KDE$, $\omega_2$ the circle with center $F$ and radius $FE$, and $\omega_3$ the circle
with center $G$ and radius $GD$.
Prove that $\omega_1$, $\omega_2$, and $\omega_3$ pass through the same point and that this point of intersection lies on the line $AK$.
10 replies
Lukaluce
May 8, 2022
s27_SaparbekovUmar
an hour ago
Assam Mathematics Olympiad 2022 Category III Q12
SomeonecoolLovesMaths   2
N an hour ago by nyacide
A particle is in the origin of the Cartesian plane. In each step the particle can go $1$ unit in any of the directions, left, right, up or down. Find the number of ways to go from $(0, 0)$ to $(0, 2)$ in $6$ steps. (Note: Two paths where identical set of points is traversed are considered different if the order of traversal of each point is different in both paths.)
2 replies
SomeonecoolLovesMaths
Sep 12, 2024
nyacide
an hour ago
Cyclic inequality with rational functions
MathMystic33   2
N 2 hours ago by navi_09220114
Source: 2025 Macedonian Team Selection Test P3
Let \(x_1,x_2,x_3,x_4\) be positive real numbers. Prove the inequality
\[
\frac{x_1 + 3x_2}{x_2 + x_3}
\;+\;
\frac{x_2 + 3x_3}{x_3 + x_4}
\;+\;
\frac{x_3 + 3x_4}{x_4 + x_1}
\;+\;
\frac{x_4 + 3x_1}{x_1 + x_2}
\;\ge\;8.
\]
2 replies
MathMystic33
Yesterday at 6:00 PM
navi_09220114
2 hours ago
f(f(n))=2n+2
Jackson0423   1
N 2 hours ago by jasperE3
Source: 2013 KMO Second Round

Let \( f : \mathbb{N} \to \mathbb{N} \) be a function satisfying the following conditions for all \( n \in \mathbb{N} \):
\[
\begin{cases}
f(n+1) > f(n) \\
f(f(n)) = 2n + 2
\end{cases}
\]Find the value of \( f(2013) \).
1 reply
Jackson0423
Yesterday at 4:07 PM
jasperE3
2 hours ago
Proving ZA=ZB
nAalniaOMliO   8
N 3 hours ago by Mathgloggers
Source: Belarusian National Olympiad 2025
Point $H$ is the foot of the altitude from $A$ of triangle $ABC$. On the lines $AB$ and $AC$ points $X$ and $Y$ are marked such that the circumcircles of triangles $BXH$ and $CYH$ are tangent, call this circles $w_B$ and $w_C$ respectively. Tangent lines to circles $w_B$ and $w_C$ at $X$ and $Y$ intersect at $Z$.
Prove that $ZA=ZH$.
Vadzim Kamianetski
8 replies
nAalniaOMliO
Mar 28, 2025
Mathgloggers
3 hours ago
Hard geometry
Lukariman   1
N 3 hours ago by Lukariman
Given circle (O) and chord AB with different diameters. The tangents of circle (O) at A and B intersect at point P. On the small arc AB, take point C so that triangle CAB is not isosceles. The lines CA and BP intersect at D, BC and AP intersect at E. Prove that the centers of the circles circumscribing triangles ACE, BCD and OPC are collinear.
1 reply
Lukariman
3 hours ago
Lukariman
3 hours ago
Geometry
AlexCenteno2007   4
N Apr 18, 2025 by sunken rock
Let ABC be an isosceles triangle with AB = AC and M the midpoint of BC. Consider a point E outside the triangle such that BE = BM and CE perpendicular to AB. The point of intersection of the perpendicular bisector of segment EB with the circumcircle of triangle AMB, which is on the same side as A with respect to BE, is point F. Show that angle FME = 90°
4 replies
AlexCenteno2007
Apr 17, 2025
sunken rock
Apr 18, 2025
Geometry
G H J
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AlexCenteno2007
153 posts
#1 • 1 Y
Y by Kizaruno
Let ABC be an isosceles triangle with AB = AC and M the midpoint of BC. Consider a point E outside the triangle such that BE = BM and CE perpendicular to AB. The point of intersection of the perpendicular bisector of segment EB with the circumcircle of triangle AMB, which is on the same side as A with respect to BE, is point F. Show that angle FME = 90°
This post has been edited 3 times. Last edited by AlexCenteno2007, Apr 17, 2025, 5:45 PM
Reason: Error
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vanstraelen
9049 posts
#2
Y by
AlexCenteno2007 wrote:
Let ABC be an isosceles triangle with AB equal to AC, and M the midpoint of side BC. Consider a point E outside the triangle such that the distance BE is equal to BM, and the distance CE is equal to CL, where L is the intersection of the perpendicular bisector of segment AB with the circumcircle of triangle AMB, on the same side as A with respect to BE. Point F is the intersection of the perpendicular bisector of segment AB with the circumcircle of triangle AMB. Show that angle FME is equal to 90°

L is the intersection of the perpendicular bisector of segment AB with the circumcircle of triangle AMB

and

Point F is the intersection of the perpendicular bisector of segment AB with the circumcircle of triangle AMB

The same sentence ?
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AlexCenteno2007
153 posts
#3
Y by
vanstraelen wrote:
AlexCenteno2007 wrote:
Let ABC be an isosceles triangle with AB equal to AC, and M the midpoint of side BC. Consider a point E outside the triangle such that the distance BE is equal to BM, and the distance CE is equal to CL, where L is the intersection of the perpendicular bisector of segment AB with the circumcircle of triangle AMB, on the same side as A with respect to BE. Point F is the intersection of the perpendicular bisector of segment AB with the circumcircle of triangle AMB. Show that angle FME is equal to 90°

L is the intersection of the perpendicular bisector of segment AB with the circumcircle of triangle AMB

and

Point F is the intersection of the perpendicular bisector of segment AB with the circumcircle of triangle AMB

The same sentence ?

My mistake
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vanstraelen
9049 posts
#4
Y by
Given $\triangle ABC\ :\ A(0,a),B(-b,0),C(b,0)$, point $M(0,0)$.

The line $CE\ :\ y=-\frac{b}{a}(x-b)$ intersects the circle $(x+b)^{2}+y^{2}=b^{2}$ in the point $E(-\frac{b(a^{2}-b^{2}+aw)}{a^{2}+b^{2}},\frac{b^{2}(2a+w)}{a^{2}+b^{2}})$
with $w=\sqrt{a^{2}-3b^{2}}$; the slope of the line $EM\ :\ m_{EM}=-\frac{b(2a+w)}{a^{2}-b^{2}+aw} \quad (1)$.

The perpendicular bisector of $BE\ :\ y=\frac{2x(aw-2b^{2})+bw(2a+w)}{2b(2a+w)}$ intersects the circumcircle $x^{2}+y^{2}+bx-ay=0$
in the point $F(\frac{bw(2a+w)}{2(a^{2}+b^{2})},\frac{w(a^{2}-b^{2}+aw)}{2(a^{2}+b^{2})})$.
The slope of the line $FM\ :\ m_{FM}=\frac{a^{2}-b^{2}+aw}{b(2a+w)}$, see (1).
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sunken rock
4394 posts
#5
Y by
Somebody really skilled in searching may find it in High School Olympiad forum!
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