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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)!

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[*]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
Looks like power mean, but it is not
Nuran2010   0
35 minutes ago
Source: Azerbaijan Al-Khwarizmi IJMO TST 2025
For $a,b,c$ positive real numbers satisfying $a^2+b^2+c^2 \geq 3$,show that:

$\sqrt[3]{\frac{a^3+b^3+c^3}{3}}+\frac{a+b+c}{9} \geq \frac{4}{3}$.
0 replies
+1 w
Nuran2010
35 minutes ago
0 replies
Taking antipode on isosceles triangle's circumcenter
Nuran2010   0
39 minutes ago
Source: Azerbaijan Al-Khwarizmi IJMO TST 2025
In isosceles triangle, the condition $AB=AC>BC$ is satisfied. Point $D$ is taken on the circumcircle of $ABC$ such that $\angle CAD=90^{\circ}$.A line parallel to $AC$ which passes from $D$ intersects $AB$ and $BC$ respectively at $E$ and $F$.Show that circumcircle of $ADE$ passes from circumcenter of $DFC$.
0 replies
Nuran2010
39 minutes ago
0 replies
R to R, with x+f(xy)=f(1+f(y))x
NicoN9   3
N 40 minutes ago by EeEeRUT
Source: Own.
Find all functions $f: \mathbb{R} \rightarrow \mathbb{R}$ such that\[
x+f(xy)=f(1+f(y))x
\]for all $x, y\in \mathbb{R}$.
3 replies
NicoN9
4 hours ago
EeEeRUT
40 minutes ago
find angle
TBazar   7
N 44 minutes ago by TBazar
Given $ABC$ triangle with $AC>BC$. We take $M$, $N$ point on AC, AB respectively such that $AM=BC$, $CM=BN$. $BM$, $AN$ lines intersect at point $K$. If $2\angle AKM=\angle ACB$, find $\angle ACB$
7 replies
TBazar
May 8, 2025
TBazar
44 minutes ago
ISI UGB 2025 P4
SomeonecoolLovesMaths   0
an hour ago
Source: ISI UGB 2025 P4
Let $S^1 = \{ z \in \mathbb{C} \mid |z| =1 \}$ be the unit circle in the complex plane. Let $f \colon S^1 \longrightarrow S^2$ be the map given by $f(z) = z^2$. We define $f^{(1)} \colon = f$ and $f^{(k+1)} \colon = f \circ f^{(k)}$ for $k \geq 1$. The smallest positive integer $n$ such that $f^{(n)}(z) = z$ is called the period of $z$. Determine the total number of points in $S^1$ of period $2025$.
(Hint : $2025 = 3^4 \times 5^2$)
0 replies
SomeonecoolLovesMaths
an hour ago
0 replies
ISI UGB 2025 P8
SomeonecoolLovesMaths   0
an hour ago
Source: ISI UGB 2025 P8
Let $n \geq 2$ and let $a_1 \leq a_2 \leq \cdots \leq a_n$ be positive integers such that $\sum_{i=1}^{n} a_i = \prod_{i=1}^{n} a_i$. Prove that $\sum_{i=1}^{n} a_i \leq 2n$ and determine when equality holds.
0 replies
SomeonecoolLovesMaths
an hour ago
0 replies
ISI UGB 2025 P6
SomeonecoolLovesMaths   0
an hour ago
Source: ISI UGB 2025 P6
Let $\mathbb{N}$ denote the set of natural numbers, and let $\left( a_i, b_i \right)$, $1 \leq i \leq 9$, be nine distinct tuples in $\mathbb{N} \times \mathbb{N}$. Show that there are three distinct elements in the set $\{ 2^{a_i} 3^{b_i} \colon 1 \leq i \leq 9 \}$ whose product is a perfect cube.
0 replies
SomeonecoolLovesMaths
an hour ago
0 replies
ISI UGB 2025 P2
SomeonecoolLovesMaths   0
an hour ago
Source: ISI UGB 2025 P2
If the interior angles of a triangle $ABC$ satisfy the equality, $$\sin ^2 A + \sin ^2 B + \sin^2  C = 2 \left( \cos ^2 A + \cos ^2 B + \cos ^2 C \right),$$prove that the triangle must have a right angle.
0 replies
SomeonecoolLovesMaths
an hour ago
0 replies
Six variables
Nguyenhuyen_AG   1
N 2 hours ago by TNKT
Let $a,\,b,\,c,\,x,\,y,\,z$ be six positive real numbers. Prove that
$$\frac{a}{b+c} \cdot \frac{y+z}{x} + \frac{b}{c+a} \cdot \frac{z+x}{y} + \frac{c}{a+b} \cdot \frac{x+y}{z} \geqslant 2+\sqrt{\frac{8abc}{(a+b)(b+c)(c+a)}}.$$
1 reply
Nguyenhuyen_AG
Today at 5:09 AM
TNKT
2 hours ago
Anything real in this system must be integer
Assassino9931   3
N 2 hours ago by Sardor_lil
Source: Al-Khwarizmi International Junior Olympiad 2025 P1
Determine the largest integer $c$ for which the following statement holds: there exists at least one triple $(x,y,z)$ of integers such that
\begin{align*} x^2 + 4(y + z) = y^2 + 4(z + x) = z^2 + 4(x + y) = c \end{align*}and all triples $(x,y,z)$ of real numbers, satisfying the equations, are such that $x,y,z$ are integers.

Marek Maruin, Slovakia
3 replies
Assassino9931
May 9, 2025
Sardor_lil
2 hours ago
Goals for 2025-2026
Airbus320-214   2
N 3 hours ago by AshAuktober
Please write down your goal/goals for competitions here for 2025-2026.
2 replies
Airbus320-214
4 hours ago
AshAuktober
3 hours ago
MOP Emails Out! (not clickbait)
Mathandski   104
N 3 hours ago by ohiorizzler1434
What an emotional roller coaster the past 34 days have been.

Congrats to all that qualified!
104 replies
Mathandski
Apr 22, 2025
ohiorizzler1434
3 hours ago
Past USAMO Medals
sdpandit   2
N 6 hours ago by sdpandit
Does anyone know where to find lists of USAMO medalists from past years? I can find the 2025 list on their website, but they don't seem to keep lists from previous years and I can't find it anywhere else. Thanks!
2 replies
sdpandit
May 8, 2025
sdpandit
6 hours ago
Geo is back??
GoodMorning   137
N Today at 5:58 AM by Siddharthmaybe
Source: 2023 USAJMO Problem 2/USAMO Problem 1
In an acute triangle $ABC$, let $M$ be the midpoint of $\overline{BC}$. Let $P$ be the foot of the perpendicular from $C$ to $AM$. Suppose that the circumcircle of triangle $ABP$ intersects line $BC$ at two distinct points $B$ and $Q$. Let $N$ be the midpoint of $\overline{AQ}$. Prove that $NB=NC$.

Proposed by Holden Mui
137 replies
GoodMorning
Mar 23, 2023
Siddharthmaybe
Today at 5:58 AM
Moving P(o)in(t)s
bobthegod78   70
N Apr 25, 2025 by Ilikeminecraft
Source: USAJMO 2021/4
Carina has three pins, labeled $A, B$, and $C$, respectively, located at the origin of the coordinate plane. In a move, Carina may move a pin to an adjacent lattice point at distance $1$ away. What is the least number of moves that Carina can make in order for triangle $ABC$ to have area 2021?

(A lattice point is a point $(x, y)$ in the coordinate plane where $x$ and $y$ are both integers, not necessarily positive.)
70 replies
bobthegod78
Apr 15, 2021
Ilikeminecraft
Apr 25, 2025
Moving P(o)in(t)s
G H J
G H BBookmark kLocked kLocked NReply
Source: USAJMO 2021/4
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bobthegod78
2982 posts
#1 • 7 Y
Y by FaThEr-SqUiRrEl, tigerzhang, samrocksnature, icematrix2, srisainandan6, megarnie, centslordm
Carina has three pins, labeled $A, B$, and $C$, respectively, located at the origin of the coordinate plane. In a move, Carina may move a pin to an adjacent lattice point at distance $1$ away. What is the least number of moves that Carina can make in order for triangle $ABC$ to have area 2021?

(A lattice point is a point $(x, y)$ in the coordinate plane where $x$ and $y$ are both integers, not necessarily positive.)
This post has been edited 2 times. Last edited by bobthegod78, Apr 15, 2021, 6:40 PM
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coolmath2017
629 posts
#2 • 20 Y
Y by fuzimiao2013, FaThEr-SqUiRrEl, EZmath2006, samrocksnature, icematrix2, megarnie, rayfish, centslordm, hwdaniel, Toinfinity, mathking999, minusonetwelth, Jndd, Ritwin, mathmax12, EpicBird08, thinkcow, sophiawang85, Yiyj1, Sedro
It's not 133 :(
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Lcz
390 posts
#3 • 8 Y
Y by FaThEr-SqUiRrEl, samrocksnature, icematrix2, centslordm, megarnie, Ritwin, channing421, TheHimMan
The answer was $128$.

You basically make optimizations to get it down to (wlog) $A=(a,d)$, $B=(b,-e)$, $C=(-c,f)$ where one of $a,b$ is $0$ and one of $(d,f)$ is $0$, and $a,b,c,d,e,f \geq 0$, and then casework shoelace: there are two cases,

(1, where $a=d=0$) $wx-yz=4042$, find the minimum possible value of $w+x+y+z$
(2, else) $(w+x)(y+z)-wz=4042$, find the minimum possible value of $w+x+y+z$

and from here it is clear because $63*64=4032<4042$.

Why do I feel like this was a rejected hmmt proposal or something ;)
This post has been edited 1 time. Last edited by Lcz, Apr 15, 2021, 5:12 PM
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IAmTheHazard
5001 posts
#5 • 5 Y
Y by FaThEr-SqUiRrEl, samrocksnature, icematrix2, centslordm, megarnie
Pretty hard, especially finding the construction. You can show that either one vertex is the origin and the other two are in opposite quadrants (quadrants here include the axes bounding them) or two of the vertices are on one of each axis and the third is in the quadrant not containing either of the other two. Then shoelace and use extremely weak inequalities and a bit of AM-GM to get that you need at least 128.
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amuthup
779 posts
#6 • 7 Y
Y by FaThEr-SqUiRrEl, hrithikguy, samrocksnature, aie8920, icematrix2, centslordm, hwdaniel
The answer is $\boxed{128},$ achieved by moving $A$ to $(-10,0),$ moving $B$ to $(54,-1),$ and moving $C$ to $(0,63).$

We may assume Carina performs all horizontal moves before vertical moves, as this affects neither the final positions of the pins nor the number of moves necessary. Suppose that after Carina has performed all horizontal moves, the pins are at $(x_1,0),(x_2,0),$ and $(x_3,0)$ respectively.

$\textbf{Claim: }$ We may assume WLOG that $x_1\le0=x_2\le x_3.$

$\emph{Proof: }$ Suppose for the sake of contradiction that $x_1\le 0$ and $x_3\ge x_2\ge 0.$ Then, Carina performed at least $-x_1+x_2+x_3$ horizontal moves. If Carina had instead moved the pins to $(x_1-x_2,0),(0,0),$ and $(x_3-x_2,0)$ (which wouldn't affect their relative positions), then she would have performed $$(x_2-x_1)+(x_3-x_2)=x_3-x_1<-x_1+x_2+x_3$$horizontal moves.

The case $x_3\ge x_2\ge 0$ can be dealt with similarly, so it is always optimal for $x_1\le 0=x_2\le x_3.$ $\blacksquare$

Now let the y-coordinates of the pins be $y_1,y_2,y_3$ respectively. By Shoelace, $$[ABC]=\frac{1}{2}\left|\underline{(x_1y_2+x_3y_1)-(x_3y_2+x_1y_3)}\right|.$$Immediately after Carina has performed all horizontal moves, the underlined expression is $0.$ Moreover,
  • Increasing $y_1$ by $1$ increases the expression by $x_3$
  • Increasing $y_2$ by $1$ increases the expression by $x_1-x_3$
  • Increasing $y_3$ by $1$ increases the expression by $-x_1,$
and the opposite is true for decreasing $y$-coordinates.

Therefore, in order for the expression to reach $\pm 4042,$ Carina must perform at least $$\left\lceil\frac{4042}{\max(|x_3|,|x_1-x_3|,|-x_1|)}\right\rceil=\left\lceil\frac{4042}{x_3-x_1}\right\rceil$$vertical moves.

This yields a total of $$(x_3-x_1)+\left\lceil\frac{4042}{x_3-x_1}\right\rceil$$moves.

It is easy to check that this expression has a minimum of $128,$ as desired.
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SKeole
417 posts
#7 • 3 Y
Y by FaThEr-SqUiRrEl, samrocksnature, icematrix2
I believe the answer was 128
My construction: (5, 1); (-52, 0); and (0, -70)

the maximum area you can create with 127 moves is 63*64/2=2016
This post has been edited 1 time. Last edited by SKeole, Apr 15, 2021, 5:33 PM
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star32
165 posts
#8 • 4 Y
Y by FaThEr-SqUiRrEl, samrocksnature, icematrix2, hwdaniel
This problem was so harddddd for its position(I was able to solve it but took me quite some time :( )
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Awesome_guy
862 posts
#9 • 3 Y
Y by FaThEr-SqUiRrEl, samrocksnature, icematrix2
How many points is a correct proof and answer but no construction?
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brianzjk
1201 posts
#10 • 5 Y
Y by Awesome_guy, FaThEr-SqUiRrEl, samrocksnature, icematrix2, megarnie
Awesome_guy wrote:
How many points is a correct proof and answer but no construction?

usually this would be a 6
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DottedCaculator
7353 posts
#11 • 7 Y
Y by FaThEr-SqUiRrEl, samrocksnature, icematrix2, megarnie, AnikaMehta, Mango247, Yiyj1
I proved that the maximum area after n moves is n^2/8 by shoelace bash
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lethan3
907 posts
#12 • 3 Y
Y by FaThEr-SqUiRrEl, samrocksnature, icematrix2
wow bob you took jmo? you're like in 7th right?

I basically considered x and y coordinates separately, showed the median of the x coordinates is 0 to be optimal and same for y, then shoelaced, factored, and stuff to get 128
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asbodke
1914 posts
#13 • 3 Y
Y by FaThEr-SqUiRrEl, samrocksnature, icematrix2
This was the only problem I got :/

I showed that no two of $A,B,C$ can be in in the same direction in any axis, and then there were only 3 cases: the one where $C$ goes both left and down, which we can reduce to $C$ being only moving in one direction. Then all 3 move in only one direction, which we can use AM-GM on easily.

If $C$ doesn't move at all, it's just a right triangle.
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DottedCaculator
7353 posts
#14 • 8 Y
Y by vvluo, FaThEr-SqUiRrEl, samrocksnature, icematrix2, megarnie, AnikaMehta, Lionking212, Yiyj1
I’m pretty sure my construction was (-6,-9),(58,0),(0,55)
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Leonard_my_dude
117 posts
#15 • 4 Y
Y by FaThEr-SqUiRrEl, samrocksnature, icematrix2, Mango247
Wait what to do after getting ab + ac + bd = 4042
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lethan3
907 posts
#16 • 4 Y
Y by Leonard_my_dude, FaThEr-SqUiRrEl, samrocksnature, icematrix2
add cd to both sides
Z K Y
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a