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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
Challenge: Make every number to 100 using 4 fours
CJB19   118
N 5 minutes ago by pingpongmerrily
I've seen this attempted a lot but I want to see if the AoPS community can actually do it. Using ONLY 4 fours and math operations, make as many numbers as you can. Try to go in order. I'll start:
$$(4-4)*4*4=0$$$$4-4+4/4=1$$$$4/4+4/4=2$$$$(4+4+4)/4=3$$$$4+(4-4)*4=4$$$$4+4^(4-4)=5$$$$4!/4+4-4=6$$$$4+4-4/4=7$$$$4+4+4-4=8$$
I can't get the exponent in 5 to work if someone knows how to fix it please tell me
118 replies
CJB19
Thursday at 4:02 PM
pingpongmerrily
5 minutes ago
Bogus Proof Marathon
pifinity   7622
N 6 minutes ago by ToughGazelle36
Hi!
I'd like to introduce the Bogus Proof Marathon.

In this marathon, simply post a bogus proof that is middle-school level and the next person will find the error. You don't have to post the real solution :P

Use classic Marathon format:
[hide=P#]a1b2c3[/hide]
[hide=S#]a1b2c3[/hide]


Example posts:

P(x)
-----
S(x)
P(x+1)
-----
Let's go!! Just don't make it too hard!
7622 replies
pifinity
Mar 12, 2018
ToughGazelle36
6 minutes ago
How do you guys get better at competition math?
CJB19   18
N 16 minutes ago by tonu
I'm really trying to improve my math abilities because next year is my last chance to qual for mathcounts natitionals, I've gotten The Art of Problem Solving Volume 1: The basics and The Three Year Mathcounts Marathon, I've been working on Alcumus and Mathcounts trainer, and I'm going to take a Mathcounts advanced course in the fall, but are there any other things you guys use to get better?
18 replies
CJB19
May 15, 2025
tonu
16 minutes ago
2025 Mathcounts Nationals Journal
Andyluo   27
N 17 minutes ago by ZMB038
Friday May 9th

I spent my evening after school, packing for the trip, using the checklist given by my coach.
I didn’t do much preparation, as I was mostly chilling out for the upcoming days.

I also played basketball with my cousin, Kevin, who met Gotham Chess and stayed at his home!


Saturday, May 10th

I woke up at 5:30 AM, ate a light breakfast, and headed out to the airport with my luggage.

I met my teacher, but was surprised that Archishman split up with his own family.
Waiting for the TSA was pretty boring, but we soon got through, and after I found our gate.

A couple of minutes pass by, as I review an AOPS mock where I meet Archischman;
Afterward, we chill out, watch the rube goldberg machine in the airport, and wait to board the plane.

During the plane ride, I played games; however, during our descent, I heard a loud crack, and our plane started wobbling, and we heard cracking sounds in the seats. Fortunately, we were able to land and were able to attend the competition the next day.

After this, heading out, we went to the shuttle; however, we had 35 minutes. We tried to solve the Jane Street card puzzle but failed, and ended up socializing.

After we arrived at the hotel, we received a MASSIVE amount of stuff, like calculators, shirts, coupons, plaques, stickers, etc.
I also saw and got a signature from Richard Rusczyk, which was really cool.

Then, we went to a restaurant named “Chinatown Garden”, with the worst food I’ve ever had.

We then chilled in our rooms, studied for a bit, and started organizing plans for pin trading.

Our goal was to scam as many people as possible by doing 2:1 trades, as we had a “limited”
amount of pins. (We even got 5:1 and 10:1 trades)
A Virginia kid scammed me with a STEM pin, so I chased him down and got our pin back.

We got through around half the states organizing in and out of what pins we had.

Finally, we got some food from the buffet (which was surprisingly decent) and had a good time trading some more.

We ended the day with a short and brief CDR, where we had some fun, and then we went to sleep to anticipate the next day.

At night, I showered and sang karaoke with Archi.

Sunday, May 11th

Getting ready, I found out that a mock (outside the box) was recently released and took it through breakfast.

Then, once we got there at 8:30, there was a mob of parents taking pictures, and music played.

Then every team did introductions/attendance and their chants, most of which were really cringe.

I took the test; however was too slow on the sprint round and got a predicted 16.

On the target round, I was able to get through and got a 12, despite barely not solving p8 to my frustration.

Team round we did decently, scoring a 14/20, which was one of the best scores around us, that even orz states like Texas and Washington didn’t beat.

I predicted around a 28 with the answer key.

After this, we teamed up with North Carolina (chill af) and went to a pho shop (54 Restaurant), which tasted amazing. (A far contrast from Chinatown Garden)

Then, we went to an aerospace museum, where we played Brawl Stars and went around. Eventually, we saw models of blackholes and air vacuums, and played a flight simulator.

Then we went to our hotel, chilled, and watched basketball games.

After, we went to an Indian restaurant named “Himilayan Doko” which was really delicious!

Then we raided different rooms, from NC, HAWAII, Idaho, Virgin Islands, and accidentally a random dudes room who was ticked at us.

Finally, we chilled and went to sleep, though I tried to get Henry and Archi to sleep since they were being annoying.

Monday, May 12th

We start the day forming my pin badge, and then we went to get some breakfast.

After that, we met in the breakfast area with 2 teams for table, and I actually got a 10:1 pin trade which was pretty cool.

After that, we lined up and got our thunderstick/clapping machines, and ran through the entrance of the CDR.

Sadly, we didn’t win anything, but it was cool seeing the results.

Then, we started to watch the CDR, which was really exciting.
It got really interesting when everyone saw Nathan Liu cook his opponent in half a second.

In the semifinals, it was insane, and Advait and Nathan, buzzed every question that was around mid-sprint level.

Then, it finished with Nathan beating Brandon with a 2-second solve, absolute insanity.

Finally, we went back to our rooms and got lunch in the hotel.
A few hours later, we received our scores, and I had bombed, scoring a 26 with 7 sillies. (ouch)

Unfortunately, my teammates Henry and Archishman sillied a bunch of questions.

After, we played Brawl Stars, and went to explore the hotel, where we went up a random staircase and got stuck. We went to the roof, but got scared and yelled out for help on the gym floor. Thankfully, we got back, and I went and reviewed the test.

After we reviewed the test, and went to the Mathcounts Party.

The food was mid, but the games were pretty fun.

We met a bunch of people, played air hockey, foosball, and basketball, while listening to the not so great music in the background.

Then we went back to our rooms at 8PM, to put our pins on, and I got 38/56!

Finally, we met up in a room with a bunch of Cali, and NC kids, and talked about the test, the people, and played Brawl Stars. Even Josh Frost came up to us and asked us how the trip was.

Tuesday, May 13th

I started the day waking up at 6:20, and packed up and ate breakfast. After that, Henry was late, so we packed food for him and went to the bus shuttle.

Eventually, we arrived at the airport, went through security (which was suspiciously fast), and played Brawl Stars. We also ate five guys fries, which was pretty good. Eventually, we had to part our ways with Henry and headed out to our flights, which marked the end of the trip.

Conclusion:

Although we didn’t do amazingly well in the contest, going to DC was an amazing experience. I got to meet people who were passionate about math, and hang out with them, goofing around.

This was the best math contest experience that I’ll likely ever have, and I’m glad I went through it.
27 replies
Andyluo
May 13, 2025
ZMB038
17 minutes ago
Find the minimum
sqing   7
N 18 minutes ago by sqing
Source: China Shandong High School Mathematics Competition 2025 Q4
Let $ a,b,c>0,abc>1$. Find the minimum value of $ \frac {abc(a+b+c+8)}{abc-1}. $
7 replies
sqing
6 hours ago
sqing
18 minutes ago
Insspired by Shandong 2025
sqing   5
N 21 minutes ago by sqing
Source: Own
Let $ a,b,c>0,abc>1$. Prove that$$ \frac {abc(a+b+c+ab+bc+ca+3)}{  abc-1}\geq \frac {81}{4}$$$$  \frac {abc(a+b+c+ab+bc+ca+abc+2)}{  abc-1}\geq  12+8\sqrt{2}$$
5 replies
sqing
6 hours ago
sqing
21 minutes ago
Bound of number of connected components
a_507_bc   3
N an hour ago by MmdMathLover
Source: St. Petersburg 2023 11.7
Let $G$ be a connected graph and let $X, Y$ be two disjoint subsets of its vertices, such that there are no edges between them. Given that $G/X$ has $m$ connected components and $G/Y$ has $n$ connected components, what is the minimal number of connected components of the graph $G/(X \cup Y)$?
3 replies
a_507_bc
Aug 12, 2023
MmdMathLover
an hour ago
A circle tangent to the circumcircle, excircles related
kosmonauten3114   0
2 hours ago
Source: My own, maybe well-known
Let $ABC$ be a scalene triangle with excircles $\odot(I_A)$, $\odot(I_B)$, $\odot(I_C)$. Let $\odot(A')$ be the circle which touches $\odot(I_B)$ and $\odot(I_C)$ and passes through $A$, and whose center $A'$ lies outside of the excentral triangle of $\triangle{ABC}$. Define $\odot(B')$ and $\odot(C')$ cyclically. Let $\odot(O')$ be the circle externally tangent to $\odot(A')$, $\odot(B')$, $\odot(C')$.

Prove that $\odot(O')$ is tangent to the circumcircle of $\triangle{ABC}$ at the anticomplement of the Feuerbach point of $\triangle{ABC}$.
0 replies
kosmonauten3114
2 hours ago
0 replies
Bounds on degree of polynomials
Phorphyrion   4
N 2 hours ago by Kingsbane2139
Source: 2020 Israel Olympic Revenge P3
For each positive integer $n$, define $f(n)$ to be the least positive integer for which the following holds:

For any partition of $\{1,2,\dots, n\}$ into $k>1$ disjoint subsets $A_1, \dots, A_k$, all of the same size, let $P_i(x)=\prod_{a\in A_i}(x-a)$. Then there exist $i\neq j$ for which
\[\deg(P_i(x)-P_j(x))\geq \frac{n}{k}-f(n)\]
a) Prove that there is a constant $c$ so that $f(n)\le c\cdot \sqrt{n}$ for all $n$.

b) Prove that for infinitely many $n$, one has $f(n)\ge \ln(n)$.
4 replies
Phorphyrion
Jun 11, 2022
Kingsbane2139
2 hours ago
A point on BC
jayme   7
N 2 hours ago by jayme
Source: Own ?
Dear Mathlinkers,

1. ABC a triangle
2. 0 the circumcircle
3. D the pole of BC wrt 0
4. B', C' the symmetrics of B, C wrt AC, AB
5. 1b, 1c the circumcircles of the triangles BB'D, CC'D
6. T the second point of intersection of the tangent to 1c at D with 1b.

Prove : B, C and T are collinear.

Sincerely
Jean-Louis
7 replies
jayme
Today at 6:08 AM
jayme
2 hours ago
Zack likes Moving Points
pinetree1   73
N 3 hours ago by NumberzAndStuff
Source: USA TSTST 2019 Problem 5
Let $ABC$ be an acute triangle with orthocenter $H$ and circumcircle $\Gamma$. A line through $H$ intersects segments $AB$ and $AC$ at $E$ and $F$, respectively. Let $K$ be the circumcenter of $\triangle AEF$, and suppose line $AK$ intersects $\Gamma$ again at a point $D$. Prove that line $HK$ and the line through $D$ perpendicular to $\overline{BC}$ meet on $\Gamma$.

Gunmay Handa
73 replies
pinetree1
Jun 25, 2019
NumberzAndStuff
3 hours ago
Domain and Inequality
Kunihiko_Chikaya   1
N 3 hours ago by Mathzeus1024
Source: 2018 The University of Tokyo entrance exam / Humanities, Problem 1
Define on a coordinate plane, the parabola $C:y=x^2-3x+4$ and the domain $D:y\geq x^2-3x+4.$
Suppose that two lines $l,\ m$ passing through the origin touch $C$.

(1) Let $A$ be a mobile point on the parabola $C$. Let denote $L,\ M$ the distances between the point $A$ and the lines $l,\ m$ respectively. Find the coordinate of the point $A$ giving the minimum value of $\sqrt{L}+\sqrt{M}.$

(2) Draw the domain of the set of the points $P(p,\ q)$ on a coordinate plane such that for all points $(x,\ y)$ over the domain $D$, the inequality $px+qy\leq 0$ holds.
1 reply
Kunihiko_Chikaya
Feb 25, 2018
Mathzeus1024
3 hours ago
JBMO TST Bosnia and Herzegovina 2020 P1
Steve12345   3
N 3 hours ago by AylyGayypow009
Determine all four-digit numbers $\overline{abcd}$ which are perfect squares and for which the equality holds:
$\overline{ab}=3 \cdot \overline{cd} + 1$.
3 replies
1 viewing
Steve12345
Aug 10, 2020
AylyGayypow009
3 hours ago
Problem3
samithayohan   116
N 3 hours ago by fearsum_fyz
Source: IMO 2015 problem 3
Let $ABC$ be an acute triangle with $AB > AC$. Let $\Gamma $ be its circumcircle, $H$ its orthocenter, and $F$ the foot of the altitude from $A$. Let $M$ be the midpoint of $BC$. Let $Q$ be the point on $\Gamma$ such that $\angle HQA = 90^{\circ}$ and let $K$ be the point on $\Gamma$ such that $\angle HKQ = 90^{\circ}$. Assume that the points $A$, $B$, $C$, $K$ and $Q$ are all different and lie on $\Gamma$ in this order.

Prove that the circumcircles of triangles $KQH$ and $FKM$ are tangent to each other.

Proposed by Ukraine
116 replies
samithayohan
Jul 10, 2015
fearsum_fyz
3 hours ago
Show that the expression is divisable by 5
Deomad123   5
N Apr 22, 2025 by Maxklark
This was taken from a junior math competition.
$$5|3^{2009} - 7^{2007}$$
5 replies
Deomad123
Mar 25, 2025
Maxklark
Apr 22, 2025
Show that the expression is divisable by 5
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Deomad123
5 posts
#1
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This was taken from a junior math competition.
$$5|3^{2009} - 7^{2007}$$
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HacheB2031
396 posts
#2
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sol
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xHypotenuse
783 posts
#3
Y by
What is with all of these divisability questions
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SomeonecoolLovesMaths
3262 posts
#4
Y by
Using FLT,
$3^{4} \equiv 1 \pmod 5 \Longrightarrow 3^{2009} \equiv 3 \pmod 5$
$7^{4} \equiv 1 \pmod 5 \Longrightarrow 7^{2007} \equiv 7^4 \equiv 3 \pmod 5$
Thus, $$5|3^{2009} - 7^{2007}$$
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exp-ipi-1
1074 posts
#5
Y by
$3^{2009} \equiv (-2)^{2009} \pmod 5$ and $7^{2007} \equiv 2^{2007} \pmod 5$, so $3^{2009}-7^{2007} \equiv (-2)^{2009}-2^{2007} = (-2)^{2007}(4+1) = (-2)^{2007} * 5 \equiv 0 \pmod 5$
This post has been edited 3 times. Last edited by exp-ipi-1, Mar 28, 2025, 1:19 PM
Reason: Ts pmo
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Maxklark
6 posts
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