Happy Memorial Day! Please note that AoPS Online is closed May 24-26th.

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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
old and easy imo inequality
Valentin Vornicu   216
N 9 minutes ago by alexanderchew
Source: IMO 2000, Problem 2, IMO Shortlist 2000, A1
Let $ a, b, c$ be positive real numbers so that $ abc = 1$. Prove that
\[ \left( a - 1 + \frac 1b \right) \left( b - 1 + \frac 1c \right) \left( c - 1 + \frac 1a \right) \leq 1.
\]
216 replies
Valentin Vornicu
Oct 24, 2005
alexanderchew
9 minutes ago
Tangent to incircles.
dendimon18   7
N 26 minutes ago by Gggvds1
Source: ISR 2021 TST1 p.3
Let $ABC$ be an acute triangle with orthocenter $H$. Prove that there is a line $l$ which is parallel to $BC$ and tangent to the incircles of $ABH$ and $ACH$.
7 replies
dendimon18
May 4, 2022
Gggvds1
26 minutes ago
Problem 3 of RMO 2006 (Regional Mathematical Olympiad-India)
makar   36
N 31 minutes ago by SomeonecoolLovesMaths
Source: Elementry inequality
If $ a,b,c$ are three positive real numbers, prove that $ \frac {a^{2}+1}{b+c}+\frac {b^{2}+1}{c+a}+\frac {c^{2}+1}{a+b}\ge 3$
36 replies
makar
Sep 13, 2009
SomeonecoolLovesMaths
31 minutes ago
Three numbers cannot be squares simultaneously
WakeUp   40
N 33 minutes ago by Adywastaken
Source: APMO 2011
Let $a,b,c$ be positive integers. Prove that it is impossible to have all of the three numbers $a^2+b+c,b^2+c+a,c^2+a+b$ to be perfect squares.
40 replies
WakeUp
May 18, 2011
Adywastaken
33 minutes ago
A suspcious assumption
NamelyOrange   2
N Yesterday at 1:30 AM by maromex
Let $a,b,c,d$ be positive integers. Maximize $\max(a,b,c,d)$ if $a+b+c+d=a^2-b^2+c^2-d^2=2012$.
2 replies
NamelyOrange
Thursday at 1:53 PM
maromex
Yesterday at 1:30 AM
Got what it takes to disprove Euler?
4everwise   18
N May 21, 2025 by P162008
One of Euler's conjectures was disproved in then 1960s by three American mathematicians when they showed there was a positive integer $ n$ such that \[133^5 + 110^5 + 84^5 + 27^5 = n^5.\]Find the value of $ n$.
18 replies
4everwise
Feb 20, 2006
P162008
May 21, 2025
2018 Mock ARML I --7 2^n | \prod^{2048}_{k=0} C(2k , k)
parmenides51   3
N May 21, 2025 by MathIQ.
Find the largest integer $n$ such that $2^n$ divides $\prod^{2048}_{k=0} {2k \choose k}$.
3 replies
parmenides51
Jan 17, 2024
MathIQ.
May 21, 2025
Pell's Equation
Entrepreneur   0
May 19, 2025
A Pells Equation is defined as follows $$x^2-1=ky^2.$$Where $x,y$ are positive integers and $k$ is a non-square positive integer. If $(x_n,y_n)$ denotes the n-th set of solution to the equation with $(x_0,y_0)=(1,0).$ Then, prove that $$x_{n+1}x_n-ky_{n+1}y_n=x_1,$$$$x_n\pm y_n\sqrt k=(x_1\pm y_1\sqrt k)^n.$$
0 replies
Entrepreneur
May 19, 2025
0 replies
Diophantine Equation (cousin of Mordell)
urfinalopp   4
N May 18, 2025 by FoeverResentful
Find pairs of integers $(x;y)$ such that:

$x^2=y^5+32$
4 replies
urfinalopp
May 18, 2025
FoeverResentful
May 18, 2025
p+2^p-3=n^2
tom-nowy   1
N May 18, 2025 by urfinalopp
Let $n$ be a natural number and $p$ be a prime number. How many different pairs $(n, p)$ satisfy the equation:
$$p + 2^p - 3 = n^2 .$$
Inspired by https://artofproblemsolving.com/community/c4h3560823
1 reply
tom-nowy
May 18, 2025
urfinalopp
May 18, 2025
Perfect cubes
Entrepreneur   6
N May 18, 2025 by NamelyOrange
Find all ordered pairs of positive integers $(a,b,c)$ such that $\overline{abc}$ and $\overline{cab}$ are both perfect cubes.
6 replies
Entrepreneur
May 18, 2025
NamelyOrange
May 18, 2025
Exponents of integer question
Dheckob   4
N May 18, 2025 by LeYohan
Find the smallest positive integer $m$ such that $5m$ is an exact 5th power, $6m$ is an exact 6th power, and $7m$ is an exact 7th power.
4 replies
Dheckob
Apr 12, 2017
LeYohan
May 18, 2025
2017 DMI Individual Round - Downtown Mathematics Invitational
parmenides51   14
N May 18, 2025 by SomeonecoolLovesMaths
p1. Compute the smallest positive integer $x$ such that $351x$ is a perfect cube.


p2. A four digit integer is chosen at random. What is the probability all $4$ digits are distinct?


p3. If $$\frac{\sqrt{x + 1}}{\sqrt{x}}+ \frac{\sqrt{x}}{\sqrt{x + 1}} =\frac52.$$Solve for $x$.


p4. In $\vartriangle ABC$, $AB = 13$, $BC = 14$, and $AC = 15$. Let $D$ be the point on $BC$ such that $AD \perp BC$, and let $E$ be the midpoint of $AD$. If $F$ is a point such that $CDEF$ is a rectangle, compute the area of $\vartriangle AEF$.


p5. Square $ABCD$ has a sidelength of $4$. Points $P$, $Q$, $R$, and $S$ are chosen on $AB$, $BC$, $CD$, and $AD$ respectively, such that $AP$, $BQ$, $CR$, and $DS$ are length $1$. Compute the area of quadrilateral $P QRS$.


p6. A sequence $a_n$ satisfies for all integers $n$, $$a_{n+1} = 3a_n - 2a_{n-1}.$$If $a_0 = -30$ and $a_1 = -29$, compute $a_{11}$.


p7. In a class, every child has either red hair, blond hair, or black hair. All but $20$ children have black hair, all but $17$ have red hair, and all but $5$ have blond hair. How many children are there in the class?


p8. An Akash set is a set of integers that does not contain two integers such that one divides the other. Compute the minimum positive integer $n$ such that the set $\{1, 2, 3, ..., 2017\}$ can be partitioned into n Akash subsets.


PS. You should use hide for answers. Collected here.
14 replies
parmenides51
Oct 2, 2023
SomeonecoolLovesMaths
May 18, 2025
2021 SMT Guts Round 5 p17-20 - Stanford Math Tournament
parmenides51   7
N May 16, 2025 by Rombo
p17. Let the roots of the polynomial $f(x) = 3x^3 + 2x^2 + x + 8 = 0$ be $p, q$, and $r$. What is the sum $\frac{1}{p} +\frac{1}{q} +\frac{1}{r}$ ?


p18. Two students are playing a game. They take a deck of five cards numbered $1$ through $5$, shuffle them, and then place them in a stack facedown, turning over the top card next to the stack. They then take turns either drawing the card at the top of the stack into their hand, showing the drawn card to the other player, or drawing the card that is faceup, replacing it with the card on the top of the pile. This is repeated until all cards are drawn, and the player with the largest sum for their cards wins. What is the probability that the player who goes second wins, assuming optimal play?


p19. Compute the sum of all primes $p$ such that $2^p + p^2$ is also prime.


p20. In how many ways can one color the $8$ vertices of an octagon each red, black, and white, such that no two adjacent sides are the same color?


PS. You should use hide for answers. Collected here.
7 replies
parmenides51
Feb 11, 2022
Rombo
May 16, 2025
Polynomial
Z_.   1
N Apr 23, 2025 by rchokler
Let \( m \) be an integer greater than zero. Then, the value of the sum of the reciprocals of the cubes of the roots of the equation
\[
mx^4 + 8x^3 - 139x^2 - 18x + 9 = 0
\]is equal to:
1 reply
Z_.
Apr 23, 2025
rchokler
Apr 23, 2025
Polynomial
G H J
G H BBookmark kLocked kLocked NReply
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Z_.
28 posts
#1
Y by
Let \( m \) be an integer greater than zero. Then, the value of the sum of the reciprocals of the cubes of the roots of the equation
\[
mx^4 + 8x^3 - 139x^2 - 18x + 9 = 0
\]is equal to:
This post has been edited 1 time. Last edited by Z_., Apr 23, 2025, 9:21 PM
Reason: .
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rchokler
2975 posts
#2
Y by
Let $a,b,c,d$ be the reciprocals of the roots. Then they solve $9x^4-18x^3-139x^2+8x+m=0$.

Then by Newton's identities, where $p_n=a^n+b^n+c^n+d^n$ and $e_n$ are elementary symmetric polynomials give:

$p_3=e_1p_2-e_2p_1+3e_3=e_1(e_1p_1-2e_2)-e_2p_1+3e_3=e_1(e_1^2-2e_2)-e_1e_2+3e_3=e_1^3-3e_1e_2+3e_3=2^3+3\cdot 2\cdot\frac{139}{9}-3\cdot\frac{8}{9}=98$
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