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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
Pertenacious Polynomial Problem
BadAtCompetitionMath21420   1
N 2 minutes ago by elizhang101412
Let the polynomial $P(x) = x^3-x^2+px-q$ have real roots and real coefficients with $q>0$. What is the maximum value of $p+q$?

This is a problem I made for my math competition, and I wanted to see if someone would double-check my work (No Mike allowed):

solution
Is this solution good?
1 reply
BadAtCompetitionMath21420
an hour ago
elizhang101412
2 minutes ago
A challenging sum
Polymethical_   0
3 minutes ago
I tried to integrate series of log(1-x) / x
0 replies
Polymethical_
3 minutes ago
0 replies
Prove that the triangle is isosceles.
TUAN2k8   4
N 30 minutes ago by JARP091
Source: My book
Given acute triangle $ABC$ with two altitudes $CF$ and $BE$.Let $D$ be the point on the line $CF$ such that $DB \perp BC$.The lines $AD$ and $EF$ intersect at point $X$, and $Y$ is the point on segment $BX$ such that $CY \perp BY$.Suppose that $CF$ bisects $BE$.Prove that triangle $ACY$ is isosceles.
4 replies
TUAN2k8
Yesterday at 9:55 AM
JARP091
30 minutes ago
Pythagoras...
Hip1zzzil   0
31 minutes ago
Source: KMO 2025 Round 1 P20
Find the sum of all $k$s such that:
There exists two odd positive integers $a,b$ such that ${k}^{2}={a}^{2b}+{(2b)}^{4}.$
0 replies
Hip1zzzil
31 minutes ago
0 replies
Hard Function
johnlp1234   2
N 39 minutes ago by maromex
Find all function $f:\mathbb{R}^{+} \rightarrow \mathbb{R}^{+}$ such that:
$$f(x^3+f(y))=y+(f(x))^3$$
2 replies
johnlp1234
Jul 8, 2020
maromex
39 minutes ago
Guangxi High School Mathematics Competition 2025 Q12
sqing   3
N 44 minutes ago by sqing
Source: China Guangxi High School Mathematics Competition 2025 Q12
Let $ a,b,c>0  $. Prove that
$$abc\geq \frac {a+b+c}{\frac {1}{a^2}+\frac {1}{b^2}+\frac {1}{c^2} }\geq(a+b-c)(b+c-a)(c+a-b)$$
3 replies
sqing
an hour ago
sqing
44 minutes ago
Hard Function
johnlp1234   4
N an hour ago by jasperE3
f:R+--->R+:
f(x^3+f(y))=y+(f(x))^3
4 replies
johnlp1234
Jul 7, 2020
jasperE3
an hour ago
Pythagorean Diophantine?
youochange   2
N an hour ago by Ianis
The number of ordered pair $(a,b)$ of positive integers with $a \le b$ satisfying $a^2+b^2=2025$ is

Click to reveal hidden text
2 replies
youochange
2 hours ago
Ianis
an hour ago
A china olympia 2015 problem.
Math2030   0
2 hours ago
Let $n \geq 5$ be a positive integer and let $A$ and $B$ be sets of integers satisfying the following conditions:

i) $|A| = n$, $|B| = m$ and $A$ is a subset of $B$
ii) For any distinct $x,y \in B$, $x+y \in B$ iff $x,y \in A$

Determine the minimum value of $m$.
0 replies
Math2030
2 hours ago
0 replies
Bounding With Powers
Shreyasharma   5
N 2 hours ago by jacosheebay
Is this a valid solution for the following problem (St. Petersburg 1996):

Find all positive integers $n$ such that,

$$ 3^{n-1} + 5^{n-1} | 3^n + 5^n$$
Solution
5 replies
Shreyasharma
Jul 11, 2023
jacosheebay
2 hours ago
Permutations of Integers from 1 to n
Twoisntawholenumber   75
N 4 hours ago by SYBARUPEMULA
Source: 2020 ISL C1
Let $n$ be a positive integer. Find the number of permutations $a_1$, $a_2$, $\dots a_n$ of the
sequence $1$, $2$, $\dots$ , $n$ satisfying
$$a_1 \le 2a_2\le 3a_3 \le \dots \le na_n$$.

Proposed by United Kingdom
75 replies
Twoisntawholenumber
Jul 20, 2021
SYBARUPEMULA
4 hours ago
Again
heartwork   11
N 4 hours ago by Mathandski
Source: Vietnam MO 2002, Problem 5
Determine for which $ n$ positive integer the equation: $ a + b + c + d = n \sqrt {abcd}$ has positive integer solutions.
11 replies
heartwork
Dec 16, 2004
Mathandski
4 hours ago
Cono Sur Olympiad 2011, Problem 3
Leicich   5
N 4 hours ago by Thelink_20
Let $ABC$ be an equilateral triangle. Let $P$ be a point inside of it such that the square root of the distance of $P$ to one of the sides is equal to the sum of the square roots of the distances of $P$ to the other two sides. Find the geometric place of $P$.
5 replies
Leicich
Aug 23, 2014
Thelink_20
4 hours ago
2021 SMT Guts Round 5 p17-20 - Stanford Math Tournament
parmenides51   7
N Yesterday at 8:05 PM by Rombo
p17. Let the roots of the polynomial $f(x) = 3x^3 + 2x^2 + x + 8 = 0$ be $p, q$, and $r$. What is the sum $\frac{1}{p} +\frac{1}{q} +\frac{1}{r}$ ?


p18. Two students are playing a game. They take a deck of five cards numbered $1$ through $5$, shuffle them, and then place them in a stack facedown, turning over the top card next to the stack. They then take turns either drawing the card at the top of the stack into their hand, showing the drawn card to the other player, or drawing the card that is faceup, replacing it with the card on the top of the pile. This is repeated until all cards are drawn, and the player with the largest sum for their cards wins. What is the probability that the player who goes second wins, assuming optimal play?


p19. Compute the sum of all primes $p$ such that $2^p + p^2$ is also prime.


p20. In how many ways can one color the $8$ vertices of an octagon each red, black, and white, such that no two adjacent sides are the same color?


PS. You should use hide for answers. Collected here.
7 replies
parmenides51
Feb 11, 2022
Rombo
Yesterday at 8:05 PM
Geometry
AlexCenteno2007   2
N Apr 19, 2025 by AlexCenteno2007
Let A, B, C, and D be four distinct points on a straight line, in that order. The circles with diameters AC and BD intersect at X and Y. The straight line XY intersects BC at Z. Let P be a point on XY distinct from Z. The straight line CP intersects the circle with diameter AC at C and M, and the straight line BP intersects the circle with diameter BD at B and N. Show that AM, DN, and XY are aligned.
2 replies
AlexCenteno2007
Apr 17, 2025
AlexCenteno2007
Apr 19, 2025
Geometry
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AlexCenteno2007
154 posts
#1
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Let A, B, C, and D be four distinct points on a straight line, in that order. The circles with diameters AC and BD intersect at X and Y. The straight line XY intersects BC at Z. Let P be a point on XY distinct from Z. The straight line CP intersects the circle with diameter AC at C and M, and the straight line BP intersects the circle with diameter BD at B and N. Show that AM, DN, and XY are aligned.
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vanstraelen
9050 posts
#2
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Given the four points $A(0,0),B(2b,0),C(2c,0),D(2d,0)$.
The circles $(x-c)^{2}+y^{2}=c^{2}$ and $(x-b-d)^{2}+y^{2}=(d-b)^{2}$ intersect in the points $X$ and $Y\ :\ x=\frac{2bd}{b-c+d}=\alpha$.
Choose the point $P(\alpha,\lambda)$.

The line $CP\ :\ y=\frac{\lambda}{\alpha-2c}(x-2c)$ intersects the first circle in the point $M$,
then $AM\ :\ y=\frac{2x(b-c)(c-d)}{\lambda(b-c+d)}$ intersects $XY$ in the point $S(\alpha,\frac{4bd(b-c)(c-d)}{\lambda(b-c+d)^{2}})$.

The line $BP\ :\ y=\frac{\lambda}{\alpha-2b}(x-2b)$ intersects the second circle in the point $N$,
then $DN\ :\ y=\frac{2b(b-c)(x-2d)}{\lambda(b-c+d)}$ intersects $XY$ in the point $S$.
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AlexCenteno2007
154 posts
#3
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How would you synthesize it? Their bash solution is very good!!
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