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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
Double Sum
P162008   0
9 minutes ago
Let $\xi = \lim_{m \to\infty} \sum_{n=4}^{m} \sum_{k=2}^{n-2} \frac{1}{\binom{n}{k}}.$ If the value of $\xi$ can be written as $\frac{m}{n}$ where $m$ and $n$ are co-prime positive integers then compute the value of $m^3 + n^3.$
0 replies
P162008
9 minutes ago
0 replies
Newton's Sum
P162008   2
N 42 minutes ago by P162008
If $\sum_{cyc} a = 7, \sum_{cyc} a^2 = 15, \sum_{cyc} a^3 = 19$ and $\sum_{cyc} a^4 = 25$ where each summation runs over $4$ variables $a,b,c$ and $d.$ Then find the value of $\sum_{cyc} a^5.$
2 replies
P162008
2 hours ago
P162008
42 minutes ago
Series + Limits
P162008   0
an hour ago
Find $\Omega = \lim_{n \to \infty} \frac{1}{n^2} \left(\sum_{i + j + k + l = n} ijkl\right) \left(\sum_{i + j + k = n} ijk\right)^{-1}.$
0 replies
P162008
an hour ago
0 replies
Polynomials
P162008   0
an hour ago
Consider the identity $\sum_{r=1}^{n} r = \frac{n(n + 1)}{2}.$ If we set $P_{1}(x) = \frac{x(x + 1)}{2}$ then it's the unique polynomial such that for all integers $n,$ $P_{1}(n) = \sum_{r=1}^{n} r.$ In general, for each positive integer k,there is a unique polynomial $P_{k}(x)$ such that $P_{k}(n) = \sum_{r=1}^{k} r^k \forall  n \in  \mathbb{Z}.$ Find the value of $P_{2010}(m)$ for $m = \frac{-1}{2}.$
0 replies
P162008
an hour ago
0 replies
Polynomials
P162008   0
an hour ago
Define a family of polynomials by $P_{0}(x) = x - 2$ and $P_{k}(x) = \left(P_{k - 1} (x)\right)^2 - 2$ if $k \geq 1$ then find the coefficient of $x^2$ in $P_{k}(x)$ in terms of $k.$
0 replies
P162008
an hour ago
0 replies
Polynomial Limit
P162008   0
2 hours ago
Let $p = \lim_{y\to\infty} \left(\frac{2}{y^2} \left(\lim_{z\to\infty} \frac{1}{z^4} \left(\lim_{x\to\infty} \frac{((y^2 + y + 1)x^k + 1)^{z^2 + z + 1} - ((z^2 + z + 1)x^k + 1)^{y^2 + y + 1}}{x^{2k}}\right)\right)\right)^y$ where $k \in N$ and $q = \lim_{n\to\infty} \left(\frac{\binom{2n}{n}. n!}{n^n}\right)^{1/n}$ where $n \in N$. Find the value of $p.q.$
0 replies
P162008
2 hours ago
0 replies
Octagon Problem
Shiyul   4
N 2 hours ago by Sid-darth-vater
The vertices of octagon $ABCDEFGH$ lie on the same circle. If $AB = BC = CD = DE = 11$ and $EF = FG = GH = HA = sqrt2$, what is the area of octagon $ABCDEFGH$?

I approached this problem by noticing that the area of the octagon is the area of the eight isoceles triangles with lengths $r$, $r$, and $sqrt2$ or 11. However, I didn't know how to find the radius. Can anyone give me a hint?
4 replies
Shiyul
4 hours ago
Sid-darth-vater
2 hours ago
Collect ...
luutrongphuc   3
N 2 hours ago by KevinYang2.71
Find all functions $f: \mathbb{R^+} \rightarrow \mathbb{R^+}$ such that:
$$f\left(f(xy)+1\right)=xf\left(x+f(y)\right)$$
3 replies
luutrongphuc
Apr 21, 2025
KevinYang2.71
2 hours ago
functional equation interesting
skellyrah   5
N 3 hours ago by jasperE3
find all functions IR->IR such that $$xf(x+yf(xy)) + f(f(y)) = f(xf(y))^2  + (x+1)f(x)$$
5 replies
skellyrah
Yesterday at 8:32 PM
jasperE3
3 hours ago
For a there exist b,c with b+c-2a = 0 mod p
Miquel-point   0
4 hours ago
Source: Kürschák József Competition 2024/3
Let $p$ be a prime and $H\subseteq \{0,1,\ldots,p-1\}$ a nonempty set. Suppose that for each element $a\in H$ there exist elements $b$, $c\in H\setminus \{a\}$ such that $b+ c-2a$ is divisible by $p$. Prove that $p<4^k$, where $k$ denotes the cardinality of $H$.
0 replies
1 viewing
Miquel-point
4 hours ago
0 replies
The ancient One-Dimensional Empire
Miquel-point   0
4 hours ago
Source: Kürschák József Competition 2024/2
The ancient One-Dimensional Empire was located along a straight line. Initially, there were no cities. A total of $n$ different point-like cities were founded one by one; from the second onwards, each newly founded city and the nearest existing city (the older one, if there were two) were declared sister cities. The surviving map of the empire shows the cities and the distances between them, but not the order in which they were founded. Historians have tried to deduce from the map that each city had at most 41 sister cities.
[list=a]
[*] For $n=10^6$, give a map from which this deduction can be made.
[*] Prove that for $n=10^{13}$, this conclusion cannot be drawn from any map.
[/list]
0 replies
Miquel-point
4 hours ago
0 replies
Cyclic quads jigsaw
Miquel-point   0
4 hours ago
Source: Kürschák József Competition 2024/1
The quadrilateral $ABCD$ is divided into cyclic quadrilaterals with pairwise disjoint interiors. None of the vertices of the cyclic quadrilaterals in the decomposition is an interior point of a side of any cyclic quadrilateral in the decomposition or of a side of the quadrilateral $ABCD$. Prove that $ABCD$ is also a cyclic quadrilateral.
0 replies
Miquel-point
4 hours ago
0 replies
A cyclic inequality
KhuongTrang   3
N 4 hours ago by paixiao
Source: own-CRUX
IMAGE
https://cms.math.ca/.../uploads/2025/04/Wholeissue_51_4.pdf
3 replies
KhuongTrang
Apr 21, 2025
paixiao
4 hours ago
Perfect polynomials
Phorphyrion   5
N 5 hours ago by Davdav1232
Source: 2023 Israel TST Test 5 P3
Given a polynomial $P$ and a positive integer $k$, we denote the $k$-fold composition of $P$ by $P^{\circ k}$. A polynomial $P$ with real coefficients is called perfect if for each integer $n$ there is a positive integer $k$ so that $P^{\circ k}(n)$ is an integer. Is it true that for each perfect polynomial $P$, there exists a positive $m$ so that for each integer $n$ there is $0<k\leq m$ for which $P^{\circ k}(n)$ is an integer?
5 replies
Phorphyrion
Mar 23, 2023
Davdav1232
5 hours ago
2023 Christmas Mock AIME #8 3x3 complex non linear system
parmenides51   2
N Feb 5, 2025 by Vivaandax
Let $a$, $b$, and $c$ be complex numbers such that they satisfy these equations:
$$abc + 4a^4 = 3$$$$abc + 2d^4 = 2$$$$abc +\frac{3c^4}{4}=-1$$If the maximum of $\left|\frac{a^2b^2c^2+1}{abc}\right|$ can be expressed as $\frac{p+\sqrt{q}}{r}$ for positive integers $p$, $q$, and $r$, find the minimum possible value of $p + q + r$.
2 replies
parmenides51
Jan 16, 2024
Vivaandax
Feb 5, 2025
2023 Christmas Mock AIME #8 3x3 complex non linear system
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parmenides51
30631 posts
#1
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Let $a$, $b$, and $c$ be complex numbers such that they satisfy these equations:
$$abc + 4a^4 = 3$$$$abc + 2d^4 = 2$$$$abc +\frac{3c^4}{4}=-1$$If the maximum of $\left|\frac{a^2b^2c^2+1}{abc}\right|$ can be expressed as $\frac{p+\sqrt{q}}{r}$ for positive integers $p$, $q$, and $r$, find the minimum possible value of $p + q + r$.
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vanstraelen
8986 posts
#2
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parmenides51 wrote:
Let $a$, $b$, and $c$ be complex numbers such that they satisfy these equations:
$$abc + 4a^4 = 3$$$$abc + 2b^4 = 2$$$$abc +\frac{3c^4}{4}=-1$$If the maximum of $\left|\frac{a^2b^2c^2+1}{abc}\right|$ can be expressed as $\frac{p+\sqrt{q}}{r}$ for positive integers $p$, $q$, and $r$, find the minimum possible value of $p + q + r$.

We find: $4a^{4}=3-abc$ and $2b^{4}=2-abc$ and $\frac{3}{4}c^{4}=-1-abc$.

Let $abc=t$; multiplying: $6t^{5}+(3-t)(2-t)(1+t)=0$
with one of the solutions: $t=-\frac{1+\sqrt{385}}{24}+ i \cdot \sqrt{\frac{95-\sqrt{385}}{288}}$.

Then $\left|t+\frac{1}{t}\right|=\frac{1+\sqrt{385}}{12}$.
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Vivaandax
79 posts
#3
Y by
Doing the same $x=abc$ substitution as @above, we get $6x^4 + x^3 - 4x^2 + x + 6 = 0$. Seeing that the polynomial is symmetric, we divide by $x^2$ and let $y = x + \frac{1}{x}$. From here, one gets the quadratic $6y^2+y-16=0$, which gives $y = \frac{-1 \pm \sqrt{385}}{12}$. Since we want the maximum absolute value, we have $$|\frac{a^2b^2c^2+1}{abc}| = |x+\frac{1}{x}| = |y| = \frac{1+\sqrt{385}}{12}$$giving the answer of $\boxed{398}$.
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