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Site Support Tech support and questions about AoPS classes and materials
Tech support and questions about AoPS classes and materials
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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]
Our full course list for upcoming classes is below:
All classes run 7:30pm-8:45pm ET/4:30pm - 5:45pm PT unless otherwise noted.

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0 replies
jlacosta
Mar 2, 2025
0 replies
solve the system of equations
Havu   4
N 3 hours ago by LeoaB411
Solve the system of equations:
\[\begin{cases}
3x^2-2xy+3y^2+\dfrac{2}{x^2-2xy+y^2}=8\\
2x+\dfrac{1}{x-y}=4
\end{cases}\]
4 replies
Havu
Yesterday at 7:52 AM
LeoaB411
3 hours ago
a/b + b/a never integer ?
MTA_2024   4
N 4 hours ago by invisibleman
Let $a$ and $b$ be 2 distinct positive integers.
Can $\frac a b +\frac b a $ be in an integer. Prove why ?
4 replies
MTA_2024
Mar 16, 2025
invisibleman
4 hours ago
The avatars are not consistent
Craftybutterfly   0
Today at 5:48 AM
Summary of the problem: The avatars are not consistent
Page URL: idk
Steps to reproduce:
1. change your avatar
2.reload a topic you posted in
3. do #2 to a different topic with your post in it
Expected behavior: Avatars are the same
Frequency: 100%
Operating system(s): MacOS
Browser(s), including version: Chrome latest version
Additional information: refreshing does not help, neither does logging out and in
0 replies
Craftybutterfly
Today at 5:48 AM
0 replies
How to add members to forums?
Bnn81351   2
N Today at 5:22 AM by Craftybutterfly
How do I add members to forums?
2 replies
Bnn81351
Today at 12:55 AM
Craftybutterfly
Today at 5:22 AM
Does there exist a function $f:\mathbb N^* \rightarrow \mathbb Z$ other than a p
kyotaro   3
N Today at 4:36 AM by quantam13
Does there exist a function $f:\mathbb N^* \rightarrow \mathbb Z$ other than a polynomial satisfying
$$f(a)-f(b) \mid a-b$$
3 replies
kyotaro
Yesterday at 10:51 AM
quantam13
Today at 4:36 AM
Inequalities
sqing   2
N Today at 2:19 AM by sqing
Let $ a,b,c\geq 2  . $ Prove that
$$(a-1)(b^2-2)(c-1) -  \frac{1}{2}abc\geq -2$$$$(a^2-2)(b-1)(c^2-2) - \frac{3}{2}abc\geq -6$$
2 replies
sqing
Yesterday at 1:42 PM
sqing
Today at 2:19 AM
2019 Chile Classification / Qualifying NMO Juniors XXXI
parmenides51   5
N Today at 1:14 AM by liyufish
p1. Consider the sequence of positive integers $2, 3, 5, 6, 7, 8, 10, 11 ...$. which are not perfect squares. Calculate the $2019$-th term of the sequence.


p2. In a triangle $ABC$, let $D$ be the midpoint of side $BC$ and $E$ be the midpoint of segment $AD$. Lines $AC$ and $BE$ intersect at $F$. Show that $3AF = AC$.


p3. Find all positive integers $n$ such that $n! + 2019$ is a square perfect.


p4. In a party, there is a certain group of people, none of whom has more than $3$ friends in this. However, if two people are not friends at least they have a friend in this party. What is the largest possible number of people in the party?
5 replies
parmenides51
Oct 11, 2021
liyufish
Today at 1:14 AM
2^n = p+3^p
reeh_haan   8
N Today at 12:20 AM by MajesticCheese
Find all pairs $(p, n)$ of positive integers which satisfy the equation $$2^n = p+3^p$$
8 replies
reeh_haan
Dec 28, 2021
MajesticCheese
Today at 12:20 AM
2017 Mock ARML Team Round #7 Revenge of the incenters
parmenides51   1
N Yesterday at 10:16 PM by Giant_PT
Let $ABC$ be a triangle with side lengths $AB = 20$, $BC = 17$, $AC = 13$, incenter $I$ and circumcircle $\Gamma$, and let $\omega_A$ be the circle that is tangent to $AB$, $AC$, $\Gamma$ at $D$ ,$E$, $F$, respectively. If $I_F$ ,$ I_I$, $I_C$ denote the incenters of $CFI$, $FIE$, $ECF$, respectively, find the measure, in degrees, of the largest angle in $\vartriangle I_F I_II_C$.
1 reply
parmenides51
Jan 12, 2024
Giant_PT
Yesterday at 10:16 PM
Don Sirloin Bowel's Algorithm
BadAtCompetitionMath21420   1
N Yesterday at 10:07 PM by ohiorizzler1434
Can you sum
\begin{align*}
    \sum_{k=1}^n F^m_k?
\end{align*}
I coined a strategy Don Sirloin Bowel's algorithm because I found it and didn't see it anywhere else. Please tell me if this looks familiar because it can have absolutely scrumptious applications. (I hope that this stuff can help you sum that.) Starting with the "golden quadratic" or whatever the sigma it's called $x^2=x+1$. Multiplying by $x$ on both sides and resubstituting $x^2$, we find $x^3=x^2+x=(x+1)+x=2x+1$. Continuing this process, we find $x^4=3x+2$, $x^5=5x+3$, and so forth. We claim that $x^n=F_nx+F_{n-1}.$ We already have our base case. $x^n=F_nx+F_{n-1}$. Multiplying by $x$, $x^{n+1}=F_nx^2+F_{n-1}x=F_n(x+1)+F_{n-1}x=F_{n+1}x+F_{n}$. Hence, we have proved our claim by induction. Now, raising both sides to the $m$th power,
\begin{align*}
    x^{mn}&=\sum_{k=0}^m \binom{m}{k}F_{n}^{m-k}F_{n-1}^kx^m\\
    &=\sum_{k=0}^m \binom{m}{k}F_{n}^{m-k}F_{n-1}^k(F_mx+F_{m-1})\\
    &=x\sum_{k=0}^m \binom{m}{k}F_{n}^{m-k}F_{n-1}^kF_m+\sum_{k=0}^mF_{n}^{m-k}F_{n-1}^kF_{m-1}\\
    &=F_{mn}x+F_{mn-1}
\end{align*}So,
\begin{align*}
    F_{mn}=\sum_{k=0}^m \binom{m}{k}F_{n}^{m-k}F_{n-1}^kF_m
\end{align*}and
\begin{align*}
    F_{mn-1}=\sum_{k=0}^mF_{n}^{m-k}F_{n-1}^kF_{m-1}
\end{align*}Are these identities useful? And can you use them to compute the sum?
1 reply
BadAtCompetitionMath21420
Yesterday at 9:50 PM
ohiorizzler1434
Yesterday at 10:07 PM
k AoPS Academy: Exporting rich format results in broken BBCode.
Minium   1
N Yesterday at 9:06 PM by jlacosta
When exporting a rich format document in the writing tab into the message board, bold formatting specifically is broken and results in broken BBCode.
Page URL: virtual.aopsacademy.org/class/<any writing class works here>/writing

TO REPRODUCE
1. enter "Lorem ipsum".
2. apply bold to "Lorem"
3. apply italic to "ip".
4. click the Post Draft on Message Board
5. read the contents of the message board post.

FOR EXAMPLE
When I format "Lorem ipsum" (in the writing tab of course), but when I export to post it, I get

[code]Lorem[/b] ipsum[/code].

Notice that the first bolding does not start, only ends.
1 reply
Minium
Mar 18, 2025
jlacosta
Yesterday at 9:06 PM
Chessboard
Ecrin_eren   5
N Yesterday at 8:44 PM by TrendCrusher
On an 8×8 checkerboard, what is the minimum number of squares that must be marked (including the marked ones) so that every square has exactly one marked neighbor? (We define neighbors as squares that share a common edge, and a square is not considered a neighbor of itself.)

5 replies
Ecrin_eren
Tuesday at 8:55 PM
TrendCrusher
Yesterday at 8:44 PM
Why does the combined equation have two negative solutions?
Luking   1
N Yesterday at 7:30 PM by vanstraelen
It is known that the moving point $G(x,y)$ is on the curve $C_1: y^2 - x^2 = 1$. There is a parabola $C_2: x^2 = 4y$ with focus $F$. Two tangent lines to$C_2$ are drawn through a point $P$ on $C1$, and the tangent points are $A$ and $B$ respectively. The line $l$ parallel to the line $AB$ is tangent to $C_2$ at point $Q$. Question: When the line $l$ and $C_1$ have two intersection points, find the range of $|QF|$.\
This may make some of the information in the question useless, because I deleted the first two questions of this big question in order to avoid making the question too long and get straight to the point.\
According to the calculation, I get the analytical expression of the line $l$ as $y=\frac{x_0}{2} x - \frac{x_0^2}{4}$.\
At first, I thought it only needed to be not parallel to the parabola asymptotes.\
That is, the slope of the straight line $k \neq \frac{a}{b}$ , then $\frac{x_0}{2} \neq \frac{a}{b}$ , so $x_0 \neq \pm \frac{2a}{b} = \pm2$ ,and $x_0^2 \neq 4$.\
$|QF| = y_0 +1 \neq 5$.\
But when I checked the answer, it was wrong.\
It combines the straight line $l$ with the curve $C_1$ to get an equation and then uses Vieta's theorem.
\begin{cases}
y=\frac{x_0}{2} x - \frac{x_0^2}{4}
x^2=4y
\end{cases}
$$( 4 x_{0}^{2}-1 6 ) y^{2}-8 x_{0}^{2} y-x_{0}^{4}-4 x_{0}^{2}=0 $$The answer is that according to the question, the equation has two negative roots. I can't understand this, and this is exactly where my problem lies.\
Then it gets the following system of equations:
\begin{cases}
4x_0-16 \neq 0
\Delta > 0
x_1+x_2 <0
x_1\cdot x_2>0
\end{cases}
Solve, $2\sqrt{5}-2<x_0<4$.
So we get $|QF|=\frac {x_0^2}{4} + 1 \in (\frac {\sqrt{5}+1}{2},2)$.
I hope you can help me figure out why both roots of that equation are negative.
IMAGE
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1 reply
Luking
Yesterday at 4:02 PM
vanstraelen
Yesterday at 7:30 PM
k How to report tags
Craftybutterfly   6
N Yesterday at 3:12 PM by Demetri
Not sure if this belongs in site support but how do you report tags for topics? I recently noticed in one of the topics I made on site support had really weird tags.
6 replies
Craftybutterfly
Yesterday at 3:30 AM
Demetri
Yesterday at 3:12 PM
AoPS Academy: Exporting rich format results in broken BBCode.
G H J
G H BBookmark kLocked kLocked NReply
The post below has been deleted. Click to close.
This post has been deleted. Click here to see post.
Minium
121 posts
#1
Y by
When exporting a rich format document in the writing tab into the message board, bold formatting specifically is broken and results in broken BBCode.
Page URL: virtual.aopsacademy.org/class/<any writing class works here>/writing

TO REPRODUCE
1. enter "Lorem ipsum".
2. apply bold to "Lorem"
3. apply italic to "ip".
4. click the Post Draft on Message Board
5. read the contents of the message board post.

FOR EXAMPLE
When I format "Lorem ipsum" (in the writing tab of course), but when I export to post it, I get

Lorem[/b] [i]ip[/i]sum
.

Notice that the first bolding does not start, only ends.
Z Y
The post below has been deleted. Click to close.
This post has been deleted. Click here to see post.
jlacosta
603 posts
#2
Y by
Thanks for letting us know. Can you email us at help@artofproblemsolving.com with a screenshot of this happening so that we can look into this for you?
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