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k a March Highlights and 2025 AoPS Online Class Information
jlacosta   0
Mar 2, 2025
March is the month for State MATHCOUNTS competitions! Kudos to everyone who participated in their local chapter competitions and best of luck to all going to State! Join us on March 11th for a Math Jam devoted to our favorite Chapter competition problems! Are you interested in training for MATHCOUNTS? Be sure to check out our AMC 8/MATHCOUNTS Basics and Advanced courses.

Are you ready to level up with Olympiad training? Registration is open with early bird pricing available for our WOOT programs: MathWOOT (Levels 1 and 2), CodeWOOT, PhysicsWOOT, and ChemWOOT. What is WOOT? WOOT stands for Worldwide Online Olympiad Training and is a 7-month high school math Olympiad preparation and testing program that brings together many of the best students from around the world to learn Olympiad problem solving skills. Classes begin in September!

Do you have plans this summer? There are so many options to fit your schedule and goals whether attending a summer camp or taking online classes, it can be a great break from the routine of the school year. Check out our summer courses at AoPS Online, or if you want a math or language arts class that doesn’t have homework, but is an enriching summer experience, our AoPS Virtual Campus summer camps may be just the ticket! We are expanding our locations for our AoPS Academies across the country with 15 locations so far and new campuses opening in Saratoga CA, Johns Creek GA, and the Upper West Side NY. Check out this page for summer camp information.

Be sure to mark your calendars for the following events:
[list][*]March 5th (Wednesday), 4:30pm PT/7:30pm ET, HCSSiM Math Jam 2025. Amber Verser, Assistant Director of the Hampshire College Summer Studies in Mathematics, will host an information session about HCSSiM, a summer program for high school students.
[*]March 6th (Thursday), 4:00pm PT/7:00pm ET, Free Webinar on Math Competitions from elementary through high school. Join us for an enlightening session that demystifies the world of math competitions and helps you make informed decisions about your contest journey.
[*]March 11th (Tuesday), 4:30pm PT/7:30pm ET, 2025 MATHCOUNTS Chapter Discussion MATH JAM. AoPS instructors will discuss some of their favorite problems from the MATHCOUNTS Chapter Competition. All are welcome!
[*]March 13th (Thursday), 4:00pm PT/7:00pm ET, Free Webinar about Summer Camps at the Virtual Campus. Transform your summer into an unforgettable learning adventure! From elementary through high school, we offer dynamic summer camps featuring topics in mathematics, language arts, and competition preparation - all designed to fit your schedule and ignite your passion for learning.[/list]
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0 replies
jlacosta
Mar 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
A nice problem
hanzo.ei   1
N 5 minutes ago by alexheinis

Given a nonzero real number \(a\) and a polynomial \(P(x)\) with real coefficients of degree \(n\) (\(n > 1\)) such that \(P(x)\) has no real roots. Prove that the polynomial
\[
Q(x) \;=\; P(x) \;+\; a\,P'(x) \;+\; a^2\,P''(x) \;+\; \dots \;+\; a^n\,P^{(n)}(x)
\]has no real roots.
1 reply
hanzo.ei
2 hours ago
alexheinis
5 minutes ago
Dear Sqing: So Many Inequalities...
hashtagmath   24
N 8 minutes ago by GreekIdiot
I have noticed thousands upon thousands of inequalities that you have posted to HSO and was wondering where you get the inspiration, imagination, and even the validation that such inequalities are true? Also, what do you find particularly appealing and important about specifically inequalities rather than other branches of mathematics? Thank you :)
24 replies
hashtagmath
Oct 30, 2024
GreekIdiot
8 minutes ago
interesting set problem
Dr.Poe98   1
N 11 minutes ago by americancheeseburger4281
Source: Brazil Cono Sur TST 2024 - T3/P3
For a pair of integers $a$ and $b$, with $0<a<b<1000$, a set $S\subset \begin{Bmatrix}1,2,3,...,2024\end{Bmatrix}$ $escapes$ the pair $(a,b)$ if for any elements $s_1,s_2\in S$ we have $\left|s_1-s_2\right| \notin \begin{Bmatrix}a,b\end{Bmatrix}$. Let $f(a,b)$ be the greatest possible number of elements of a set that escapes the pair $(a,b)$. Find the maximum and minimum values of $f$.
1 reply
Dr.Poe98
Oct 21, 2024
americancheeseburger4281
11 minutes ago
Reflection lies on incircle
MP8148   5
N 16 minutes ago by deraxenrovalo
Source: GOWACA Mock Geoly P3
In triangle $ABC$ with incircle $\omega$, let $I$ be the incenter and $D$ be the point where $\omega$ touches $\overline{BC}$. Let $S$ be the point on $(ABC)$ with $\angle ASI = 90^\circ$ and $H$ be the orthocenter of $\triangle BIC$, so that $Q \ne S$ on $\overline{HS}$ also satisfies $\angle AQI = 90^\circ$. Prove that $X$, the reflection of $I$ over the midpoint of $\overline{DQ}$, lies on $\omega$.
5 replies
MP8148
Aug 6, 2021
deraxenrovalo
16 minutes ago
Symmetric inequality FTW
Kimchiks926   20
N an hour ago by Marcus_Zhang
Source: Latvian TST for Baltic Way 2020 P1
Prove that for positive reals $a,b,c$ satisfying $a+b+c=3$ the following inequality holds:
$$ \frac{a}{1+2b^3}+\frac{b}{1+2c^3}+\frac{c}{1+2a^3} \ge 1 $$
20 replies
Kimchiks926
Oct 17, 2020
Marcus_Zhang
an hour ago
Interesting problem
V-217   0
an hour ago
On the side $(BC)$ of the triangle $ABC$ consider a mobile point $M$. Let $B'$ the orthogonal projection of $B$ on $AM$. If the mobile points $N\in (BB'$ and $P\in (AM$ are such that $ANPC$ is a paralellogram, find the locus of point $P$ when $M$ goes through $BC$.
0 replies
V-217
an hour ago
0 replies
Equilateral triangle fun
navi_09220114   6
N an hour ago by wassupevery1
Source: Own. Malaysian IMO TST 2025 P8
Let $ABC$ be an equilateral triangle, and $P$ is a point on its incircle. Let $\omega_a$ be the circle tangent to $AB$ passing through $P$ and $A$. Similarly, let $\omega_b$ be the circle tangent to $BC$ passing through $P$ and $B$, and $\omega_c$ be the circle tangent to $CA$ passing through $P$ and $C$.

Prove that the circles $\omega_a$, $\omega_b$, $\omega_c$ has a common tangent line.

Proposed by Ivan Chan Kai Chin
6 replies
navi_09220114
Today at 1:05 PM
wassupevery1
an hour ago
circle geometry solvable by many ways
Dr.Poe98   4
N an hour ago by americancheeseburger4281
Source: Brazil Cono Sur TST 2024 - T3/P4
Let $ABC$ be a triangle, $O$ its circumcenter and $\Gamma$ its circumcircle. Let $E$ and $F$ be points on $AB$ and $AC$, respectively, such that $O$ is the midpoint of $EF$. Let $A'=AO\cap \Gamma$, with $A'\ne A$. Finally, let $P$ be the point on line $EF$ such that $A'P\perp EF$. Prove that the lines $EF,BC$ and the tangent to $\Gamma$ at $A'$ are concurrent and that $\angle BPA' = \angle CPA'$.
4 replies
Dr.Poe98
Oct 21, 2024
americancheeseburger4281
an hour ago
Dealing with Multiple Circles
Wildabandon   4
N an hour ago by Double07
Source: PEMNAS Brawijaya University Senior High School Semifinal 2023 P4
A non-isosceles triangle $ABC$ and $\ell$ is tangent to the circumcircle of triangle $ABC$ through point $C$. Points $D$ and $E$ are the midpoints of segments $BC$ and $CA$ respectively, then line $AD$ and line $BE$ intersect $\ell$ at points $A_1$ and $B_1$ respectively. Line $AB_1$ and line $BA_1$ intersect the circumcircle of triangle $ABC$ at points $X$ and $Y$ respectively. Prove that $X$, $Y$, $D$ and $E$ concyclic.
4 replies
Wildabandon
Dec 1, 2024
Double07
an hour ago
Thanks u!
Ruji2018252   1
N an hour ago by pco
Jqkrjfđrfffffff
1 reply
Ruji2018252
2 hours ago
pco
an hour ago
funny title
nguyenvana   1
N an hour ago by pco
Source: no from book
Find all the functions f: R+ to R+ which satisfy the functional equation:
f(2f(x)+f(y)+xy)=xy+2x+y (x,y R+)
1 reply
nguyenvana
3 hours ago
pco
an hour ago
subsets of subset has same sum
61plus   3
N an hour ago by sttsmet
Source: 2015 China TST 2 Day 2 Q2
Set $S$ to be a subset of size $68$ of $\{1,2,...,2015\}$. Prove that there exist $3$ pairwise disjoint, non-empty subsets $A,B,C$ such that $|A|=|B|=|C|$ and $\sum_{a\in A}a=\sum_{b\in B}b=\sum_{c\in C}c$
3 replies
61plus
Mar 19, 2015
sttsmet
an hour ago
(ab)^2 + (bc)^2 + (ca)^2
GorgonMathDota   13
N 2 hours ago by ektorasmiliotis
Source: Shortlist BMO 2019, A5
Let $a,b,c$ be positive real numbers, such that $(ab)^2 + (bc)^2 + (ca)^2 = 3$. Prove that
\[ (a^2 - a + 1)(b^2 - b + 1)(c^2 - c + 1) \ge 1. \]
Proposed by Florin Stanescu (wer), România
13 replies
GorgonMathDota
Nov 7, 2020
ektorasmiliotis
2 hours ago
weird combinatorics/algebra
Dr.Poe98   1
N 2 hours ago by americancheeseburger4281
Source: Brazil Cono Sur TST 2024 - T3/P2
For each natural number $n\ge3$, let $m(n)$ be the maximum number of points inside or on the sides of a regular $n$-agon of side $1$ such that the distance between any two points is greater than $1$. Prove that $m(n)\ge n$ for $n>6$.
1 reply
Dr.Poe98
Oct 21, 2024
americancheeseburger4281
2 hours ago
Find the period
Anto0110   2
N Mar 19, 2025 by YaoAOPS
Let $a_1, a_2, ..., a_k, ...$ be a sequence that consists of an initial block of $p$ positive distinct integers that then repeat periodically. This means that $\{a_1, a_2, \dots, a_p\}$ are $p$ distinct positive integers and $a_{n+p}=a_n$ for every positive integer $n$. The terms of the sequence are not known and the goal is to find the period $p$. To do this, at each move it possible to reveal the value of a term of the sequence at your choice.
If $p$ is one of the first $k$ prime numbers, find for which values of $k$ there exist a strategy that allows to find $p$ revealing at most $8$ terms of the sequence.
2 replies
Anto0110
Mar 18, 2025
YaoAOPS
Mar 19, 2025
Find the period
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Anto0110
94 posts
#1
Y by
Let $a_1, a_2, ..., a_k, ...$ be a sequence that consists of an initial block of $p$ positive distinct integers that then repeat periodically. This means that $\{a_1, a_2, \dots, a_p\}$ are $p$ distinct positive integers and $a_{n+p}=a_n$ for every positive integer $n$. The terms of the sequence are not known and the goal is to find the period $p$. To do this, at each move it possible to reveal the value of a term of the sequence at your choice.
If $p$ is one of the first $k$ prime numbers, find for which values of $k$ there exist a strategy that allows to find $p$ revealing at most $8$ terms of the sequence.
This post has been edited 1 time. Last edited by Anto0110, Mar 18, 2025, 7:37 PM
Reason: 9
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Anto0110
94 posts
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Can anyone help?
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YaoAOPS
1497 posts
#3 • 1 Y
Y by Anto0110
Each prime $p$ must be uniquely distinguishable based off the graph on its $8$ residues connecting those residues which are the same. Conversely, we may use CRT to construct are chosen $8$ terms given a graph.

Since this graph consists of a disjoint partition of cliques we want the number of partitions of $\{1, \dots, 8\}$ into sets which can be computed as $4140$ by A000110, and this $k \le 4140$ work.
This post has been edited 1 time. Last edited by YaoAOPS, Mar 19, 2025, 2:23 PM
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