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k a May Highlights and 2025 AoPS Online Class Information
jlacosta   0
Thursday at 11:16 PM
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
Thursday at 11:16 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
No function f on reals such that f(f(x))=x^2-2
N.T.TUAN   17
N 3 minutes ago by Assassino9931
Source: VietNam TST 1990
Prove that there does not exist a function $f: \mathbb R\to\mathbb R$ such that $f(f(x))=x^2-2$ for all $x\in\mathbb R$.
17 replies
N.T.TUAN
Dec 31, 2006
Assassino9931
3 minutes ago
Hard diophant equation
MuradSafarli   4
N 5 minutes ago by iniffur
Find all positive integers $x, y, z, t$ such that the equation

$$
2017^x + 6^y + 2^z = 2025^t
$$
is satisfied.
4 replies
MuradSafarli
Yesterday at 6:12 PM
iniffur
5 minutes ago
Geometry that "looks" hard
Pmshw   3
N 18 minutes ago by Lemmas
Source: Iran 2nd round 2022 P6
we have an isogonal triangle $ABC$ such that $BC=AB$. take a random $P$ on the altitude from $B$ to $AC$.
The circle $(ABP)$ intersects $AC$ second time in $M$. Take $N$ such that it's on the segment $AC$ and $AM=NC$ and $M \neq N$.The second intersection of $NP$ and circle $(APB)$ is $X$ , ($X \neq P$) and the second intersection of $AB$ and circle $(APN)$ is $Y$ ,($Y \neq A$).The tangent from $A$ to the circle $(APN)$ intersects the altitude from $B$ at $Z$.
Prove that $CZ$ is tangent to circle $(PXY)$.
3 replies
Pmshw
May 9, 2022
Lemmas
18 minutes ago
inequalities
Cobedangiu   2
N 24 minutes ago by Cobedangiu
$a,b,c>0$ and $\sum ab=\dfrac{1}{3}$. Prove that:
$\sum \dfrac{1}{a^2-bc+1}\le 3$
2 replies
Cobedangiu
Today at 4:06 AM
Cobedangiu
24 minutes ago
IMO Genre Predictions
ohiorizzler1434   11
N 41 minutes ago by skellyrah
Everybody, with IMO upcoming, what are you predictions for the problem genres?


Personally I predict: predict
11 replies
ohiorizzler1434
5 hours ago
skellyrah
41 minutes ago
IMO Shortlist Problems
ABCD1728   6
N an hour ago by ABCD1728
Source: IMO official website
Where can I get the official solution for ISL before 2005? The official website only has solutions after 2006. Thanks :)
6 replies
ABCD1728
Yesterday at 12:44 PM
ABCD1728
an hour ago
Find the product
sqing   1
N an hour ago by Primeniyazidayi
Source: Ecrin_eren
The roots of $ x^3 - 2x^2 - 11x + k=0 $ are $r_1, r_2,  r_3 $ and $ r_1+2 r_2+3 r_3= 0.$ Find the product of all possible values of $ k .$
1 reply
sqing
2 hours ago
Primeniyazidayi
an hour ago
Some free permutation
IndoMathXdZ   23
N an hour ago by Jupiterballs
Source: ISL 2020 N7
Let $\mathcal{S}$ be a set consisting of $n \ge 3$ positive integers, none of which is a sum of two other distinct members of $\mathcal{S}$. Prove that the elements of $\mathcal{S}$ may be ordered as $a_1, a_2, \dots, a_n$ so that $a_i$ does not divide $a_{i - 1} + a_{i + 1}$ for all $i = 2, 3, \dots, n - 1$.
23 replies
IndoMathXdZ
Jul 20, 2021
Jupiterballs
an hour ago
Inspired by old results
sqing   5
N an hour ago by Novmath
Source: Own
Let $ a,b>0 , a^2+b^2+ab+a+b=5 . $ Prove that
$$ \frac{ 1 }{a+b+ab+1}+\frac{6}{a^2+b^2+ab+1}\geq \frac{7}{4}$$$$ \frac{ 1 }{a+b+ab+1}+\frac{1}{a^2+b^2+ab+1}\geq \frac{1}{2}$$$$  \frac{41}{a+b+2}+\frac{ab}{a^3+b^3+2} \geq \frac{21}{2}$$
5 replies
sqing
Apr 29, 2025
Novmath
an hour ago
Tangency geo
Assassino9931   3
N 2 hours ago by Assassino9931
Source: RMM Shortlist 2024 G1
Let $ABC$ be an acute triangle with $\angle ABC > 45^{\circ}$ and $\angle ACB > 45^{\circ}$. Let $M$ be the midpoint of the side $BC$. The circumcircle of triangle $ABM$ intersects the side $AC$ again at $X\neq A$ and the circumcircle of triangle $ACM$ intersects the side $AB$ again at $Y\neq A$. The point $P$ lies on the perpendicular bisector of the segment $BC$ so that the points $P$ and $A$ lie on the same side of $XY$ and $\angle XPY = 90^{\circ} + \angle BAC$. Prove that the circumcircles of triangles $BPY$ and $CPX$ are tangent.
3 replies
Assassino9931
Yesterday at 10:57 PM
Assassino9931
2 hours ago
Problem 6
SlovEcience   0
2 hours ago
Given two points A and B on the unit circle. The tangents to the circle at A and B intersect at point P. Then:
\[ p = \frac{2ab}{a + b} \], \[ p, a, b \in \mathbb{C} \]
0 replies
SlovEcience
2 hours ago
0 replies
cubefree divisibility
DottedCaculator   59
N 2 hours ago by SimplisticFormulas
Source: 2021 ISL N1
Find all positive integers $n\geq1$ such that there exists a pair $(a,b)$ of positive integers, such that $a^2+b+3$ is not divisible by the cube of any prime, and $$n=\frac{ab+3b+8}{a^2+b+3}.$$
59 replies
DottedCaculator
Jul 12, 2022
SimplisticFormulas
2 hours ago
Interesting inequalities
sqing   2
N 2 hours ago by sqing
Source: Own
Let $ a,b,c\geq 0 ,2a +ab +abc \geq 9. $ Prove that
$$a+b+c  \geq 4$$$$a+b+\frac{1}{4}c  \geq \frac{13}{4}$$Let $ a,b,c\geq 0 ,2a +ab +4abc \geq 9. $ Prove that
$$a+b+c+abc  \geq 4$$$$a+b+4c   \geq 4$$$$a+b+c  \geq \frac{13}{4}$$$$a+\frac{3}{2}b+4c   \geq 3(\sqrt{6}-1)$$$$a+\frac{9}{4}b+4c \geq \frac{9}{2}$$$$a+\frac{4}{3}b+4c   \geq 4\sqrt 3-\frac{8}{3}$$
2 replies
sqing
4 hours ago
sqing
2 hours ago
A convex pentagon has rational sides and equal angles
Valentin Vornicu   2
N 3 hours ago by Qing-Cloud
Source: Balkan MO 2001, problem 2
A convex pentagon $ABCDE$ has rational sides and equal angles. Show that it is regular.
2 replies
Valentin Vornicu
Apr 24, 2006
Qing-Cloud
3 hours ago
computational, segment tangent to incircle of an equilateral
parmenides51   1
N Jul 4, 2020 by rafaello
Source: All-Siberian Open School Olympiad 2014-15 11.2
On sides $AB$ and $AC$ of an equilateral triangle $ABC$ with side $10$, points $P$ and $Q$ are taken, respectively, such that the segment $PQ$ touches the circle inscribed in the triangle and its length is $4$. Find the area of the triangle $APQ$.
1 reply
parmenides51
Jul 4, 2020
rafaello
Jul 4, 2020
computational, segment tangent to incircle of an equilateral
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G H BBookmark kLocked kLocked NReply
Source: All-Siberian Open School Olympiad 2014-15 11.2
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parmenides51
30651 posts
#1 • 3 Y
Y by Mango247, Mango247, Mango247
On sides $AB$ and $AC$ of an equilateral triangle $ABC$ with side $10$, points $P$ and $Q$ are taken, respectively, such that the segment $PQ$ touches the circle inscribed in the triangle and its length is $4$. Find the area of the triangle $APQ$.
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rafaello
1079 posts
#2
Y by
My solution.

$P(APQ)=?$
Because triangle $ABC$ is equilateral, then angle bisectors, altitudes and medians coincide.
Using properties of tangents, we obtain
\[
AP+AQ=2AB-CQ-BP=2AB-AB-PQ=AB-PQ=10-4=6
\]So $P(APQ)=6+4=10$.
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