Stay ahead of learning milestones! Enroll in a class over the summer!

G
Topic
First Poster
Last Poster
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]
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.

Introductory: Grades 5-10

Prealgebra 1 Self-Paced

Prealgebra 1
Tuesday, May 13 - Aug 26
Thursday, May 29 - Sep 11
Sunday, Jun 15 - Oct 12
Monday, Jun 30 - Oct 20
Wednesday, Jul 16 - Oct 29

Prealgebra 2 Self-Paced

Prealgebra 2
Wednesday, May 7 - Aug 20
Monday, Jun 2 - Sep 22
Sunday, Jun 29 - Oct 26
Friday, Jul 25 - Nov 21

Introduction to Algebra A Self-Paced

Introduction to Algebra A
Sunday, May 11 - Sep 14 (1:00 - 2:30 pm ET/10:00 - 11:30 am PT)
Wednesday, May 14 - Aug 27
Friday, May 30 - Sep 26
Monday, Jun 2 - Sep 22
Sunday, Jun 15 - Oct 12
Thursday, Jun 26 - Oct 9
Tuesday, Jul 15 - Oct 28

Introduction to Counting & Probability Self-Paced

Introduction to Counting & Probability
Thursday, May 15 - Jul 31
Sunday, Jun 1 - Aug 24
Thursday, Jun 12 - Aug 28
Wednesday, Jul 9 - Sep 24
Sunday, Jul 27 - Oct 19

Introduction to Number Theory
Friday, May 9 - Aug 1
Wednesday, May 21 - Aug 6
Monday, Jun 9 - Aug 25
Sunday, Jun 15 - Sep 14
Tuesday, Jul 15 - Sep 30

Introduction to Algebra B Self-Paced

Introduction to Algebra B
Tuesday, May 6 - Aug 19
Wednesday, Jun 4 - Sep 17
Sunday, Jun 22 - Oct 19
Friday, Jul 18 - Nov 14

Introduction to Geometry
Sunday, May 11 - Nov 9
Tuesday, May 20 - Oct 28
Monday, Jun 16 - Dec 8
Friday, Jun 20 - Jan 9
Sunday, Jun 29 - Jan 11
Monday, Jul 14 - Jan 19

Paradoxes and Infinity
Mon, Tue, Wed, & Thurs, Jul 14 - Jul 16 (meets every day of the week!)

Intermediate: Grades 8-12

Intermediate Algebra
Sunday, Jun 1 - Nov 23
Tuesday, Jun 10 - Nov 18
Wednesday, Jun 25 - Dec 10
Sunday, Jul 13 - Jan 18
Thursday, Jul 24 - Jan 22

Intermediate Counting & Probability
Wednesday, May 21 - Sep 17
Sunday, Jun 22 - Nov 2

Intermediate Number Theory
Sunday, Jun 1 - Aug 24
Wednesday, Jun 18 - Sep 3

Precalculus
Friday, May 16 - Oct 24
Sunday, Jun 1 - Nov 9
Monday, Jun 30 - Dec 8

Advanced: Grades 9-12

Olympiad Geometry
Tuesday, Jun 10 - Aug 26

Calculus
Tuesday, May 27 - Nov 11
Wednesday, Jun 25 - Dec 17

Group Theory
Thursday, Jun 12 - Sep 11

Contest Preparation: Grades 6-12

MATHCOUNTS/AMC 8 Basics
Friday, May 23 - Aug 15
Monday, Jun 2 - Aug 18
Thursday, Jun 12 - Aug 28
Sunday, Jun 22 - Sep 21
Tues & Thurs, Jul 8 - Aug 14 (meets twice a week!)

MATHCOUNTS/AMC 8 Advanced
Sunday, May 11 - Aug 10
Tuesday, May 27 - Aug 12
Wednesday, Jun 11 - Aug 27
Sunday, Jun 22 - Sep 21
Tues & Thurs, Jul 8 - Aug 14 (meets twice a week!)

AMC 10 Problem Series
Friday, May 9 - Aug 1
Sunday, Jun 1 - Aug 24
Thursday, Jun 12 - Aug 28
Tuesday, Jun 17 - Sep 2
Sunday, Jun 22 - Sep 21 (1:00 - 2:30 pm ET/10:00 - 11:30 am PT)
Monday, Jun 23 - Sep 15
Tues & Thurs, Jul 8 - Aug 14 (meets twice a week!)

AMC 10 Final Fives
Sunday, May 11 - Jun 8
Tuesday, May 27 - Jun 17
Monday, Jun 30 - Jul 21

AMC 12 Problem Series
Tuesday, May 27 - Aug 12
Thursday, Jun 12 - Aug 28
Sunday, Jun 22 - Sep 21
Wednesday, Aug 6 - Oct 22

AMC 12 Final Fives
Sunday, May 18 - Jun 15

AIME Problem Series A
Thursday, May 22 - Jul 31

AIME Problem Series B
Sunday, Jun 22 - Sep 21

F=ma Problem Series
Wednesday, Jun 11 - Aug 27

WOOT Programs
Visit the pages linked for full schedule details for each of these programs!


MathWOOT Level 1
MathWOOT Level 2
ChemWOOT
CodeWOOT
PhysicsWOOT

Programming

Introduction to Programming with Python
Thursday, May 22 - Aug 7
Sunday, Jun 15 - Sep 14 (1:00 - 2:30 pm ET/10:00 - 11:30 am PT)
Tuesday, Jun 17 - Sep 2
Monday, Jun 30 - Sep 22

Intermediate Programming with Python
Sunday, Jun 1 - Aug 24
Monday, Jun 30 - Sep 22

USACO Bronze Problem Series
Tuesday, May 13 - Jul 29
Sunday, Jun 22 - Sep 1

Physics

Introduction to Physics
Wednesday, May 21 - Aug 6
Sunday, Jun 15 - Sep 14
Monday, Jun 23 - Sep 15

Physics 1: Mechanics
Thursday, May 22 - Oct 30
Monday, Jun 23 - Dec 15

Relativity
Mon, Tue, Wed & Thurs, Jun 23 - Jun 26 (meets every day of the week!)
0 replies
jlacosta
May 1, 2025
0 replies
Blocks in powers
mijail   3
N 2 minutes ago by Thelink_20
Source: 2022 Cono Sur #3
Prove that for every positive integer $n$ there exists a positive integer $k$, such that each of the numbers $k, k^2, \dots, k^n$ have at least one block of $2022$ in their decimal representation.

For example, the numbers 4202213 and 544202212022 have at least one block of $2022$ in their decimal representation.
3 replies
mijail
Aug 9, 2022
Thelink_20
2 minutes ago
Inequality
Sappat   9
N 6 minutes ago by bin_sherlo
Let $a,b,c$ be real numbers such that $a^2+b^2+c^2=1$. Prove that
$\frac{a^2}{1+2bc}+\frac{b^2}{1+2ca}+\frac{c^2}{1+2ab}\geq\frac{3}{5}$
9 replies
Sappat
Feb 7, 2018
bin_sherlo
6 minutes ago
An algorithm for discovering prime numbers?
Lukaluce   1
N 12 minutes ago by grupyorum
Source: 2025 Junior Macedonian Mathematical Olympiad P3
Is there an infinite sequence of prime numbers $p_1, p_2, ..., p_n, ...,$ such that for every $i \in \mathbb{N}, p_{i + 1} \in \{2p_i - 1, 2p_i + 1\}$ is satisfied? Explain the answer.
1 reply
Lukaluce
3 hours ago
grupyorum
12 minutes ago
Hard math inequality
noneofyou34   4
N 18 minutes ago by noneofyou34
If a,b,c are positive real numbers, such that a+b+c=1. Prove that:
(b+c)(a+c)/(a+b)+ (b+a)(a+c)/(c+b)+(b+c)(a+b)/(a+c)>= Sqrt.(6(a(a+c)+b(a+b)+c(b+c)) +3
4 replies
noneofyou34
5 hours ago
noneofyou34
18 minutes ago
Double integration
Tricky123   1
N Today at 4:44 AM by greenturtle3141
Q)
\[\iint_{R} \sin(xy) \,dx\,dy, \quad R = \left[0, \frac{\pi}{2}\right] \times \left[0, \frac{\pi}{2}\right]\]
How to solve the problem like this I am using the substitution method but its seems like very complicated in the last
Please help me
1 reply
Tricky123
Today at 3:51 AM
greenturtle3141
Today at 4:44 AM
Proving a group is abelian
dragosgamer12   9
N Today at 12:43 AM by ysharifi
Source: Florin Stanescu, Gazeta Matematica seria B Nr.2/2025
Let $(G,\cdot)$ be a group, $K$ a subgroup of $G$ and $f : G \rightarrow G$ an endomorphism with the following property:
There exists a nonempty set $H\subset	G$ such that for any $k \in G \setminus K$ there exist $h  \in H$ with $f(h)=k$ and $z \cdot h= h \cdot z$, for any $z \in H$.

a)Prove that $(G, \cdot)$ is abelian.
b)If, additionally, $H$ is a subgroup of $G$, prove that $H=G$
9 replies
dragosgamer12
May 15, 2025
ysharifi
Today at 12:43 AM
Convergence of complex sequence
Rohit-2006   0
Yesterday at 7:56 PM
Suppose $z_1, z_2,\cdots,z_k$ are complex numbers with absolute value $1$. For $n=1,2,\cdots$ define $w_n=z_1^n+z_2^n+\cdots+z_k^n$. Given that the sequence $(w_n)_{n\geq1}$ converges. Show that,
$$z_1=z_2=\cdots=z_k=1$$.
0 replies
Rohit-2006
Yesterday at 7:56 PM
0 replies
Problem on distinct prime divisors of P(1),...,P(n)
IAmTheHazard   3
N Yesterday at 7:04 PM by IAmTheHazard
Find all nonnegative real numbers $\lambda$ such that there exists an integer polynomial $P$ with no integer roots and a constant $c>0$ such that
$$\prod_{i=1}^n P(i)=P(1)\cdot P(2)\cdots P(n)$$has at least $cn^{\lambda}$ distinct prime divisors for all positive integers $n$.
3 replies
IAmTheHazard
Apr 4, 2025
IAmTheHazard
Yesterday at 7:04 PM
Invertible Matrices
Mateescu Constantin   7
N Yesterday at 6:27 PM by CHOUKRI
Source: Romanian District Olympiad 2018 - Grade XI - Problem 1
Show that if $n\ge 2$ is an integer, then there exist invertible matrices $A_1, A_2, \ldots, A_n \in \mathcal{M}_2(\mathbb{R})$ with non-zero entries such that:

\[A_1^{-1} + A_2^{-1} + \ldots + A_n^{-1} = (A_1 + A_2 + \ldots + A_n)^{-1}.\]
Edit.
7 replies
Mateescu Constantin
Mar 10, 2018
CHOUKRI
Yesterday at 6:27 PM
A challenging sum
Polymethical_   2
N Yesterday at 6:19 PM by GreenKeeper
I tried to integrate series of log(1-x) / x
2 replies
Polymethical_
Yesterday at 4:09 AM
GreenKeeper
Yesterday at 6:19 PM
Analytic on C excluding countably many points
Omid Hatami   12
N Yesterday at 6:13 PM by alinazarboland
Source: IMS 2009
Let $ A\subset \mathbb C$ be a closed and countable set. Prove that if the analytic function $ f: \mathbb C\backslash A\longrightarrow \mathbb C$ is bounded, then $ f$ is constant.
12 replies
Omid Hatami
May 20, 2009
alinazarboland
Yesterday at 6:13 PM
2022 Putnam A2
giginori   20
N Yesterday at 6:06 PM by dragoon
Let $n$ be an integer with $n\geq 2.$ Over all real polynomials $p(x)$ of degree $n,$ what is the largest possible number of negative coefficients of $p(x)^2?$
20 replies
giginori
Dec 4, 2022
dragoon
Yesterday at 6:06 PM
fibonacci number theory
FFA21   1
N Yesterday at 2:53 PM by alexheinis
Source: OSSM Comp'25 P3 (HSE IMC qualification)
$F_n$ fibonacci numbers ($F_1=1, F_2=1$) find all n such that:
$\forall i\in Z$ and $0\leq i\leq F_n$
$C^i_{F_n}\equiv (-1)^i\pmod{F_n+1}$
1 reply
FFA21
May 14, 2025
alexheinis
Yesterday at 2:53 PM
Tough integral
Martin.s   3
N Friday at 9:42 PM by GreenKeeper
$$\int_0^{\pi/2}\ln(\tan(\theta/2))
\;\frac{4\cos\theta\cos(2\theta)}{4\sin^4\theta+1}\,d\theta.$$
3 replies
Martin.s
May 12, 2025
GreenKeeper
Friday at 9:42 PM
Polynomial approximation and intersections
egxa   2
N Apr 29, 2025 by iliya8788
Source: All Russian 2025 10.6
What is the smallest value of \( k \) such that for any polynomial \( f(x) \) of degree $100$ with real coefficients, there exists a polynomial \( g(x) \) of degree at most \( k \) with real coefficients such that the graphs of \( y = f(x) \) and \( y = g(x) \) intersect at exactly $100$ points?
2 replies
egxa
Apr 18, 2025
iliya8788
Apr 29, 2025
Polynomial approximation and intersections
G H J
G H BBookmark kLocked kLocked NReply
Source: All Russian 2025 10.6
The post below has been deleted. Click to close.
This post has been deleted. Click here to see post.
egxa
211 posts
#1
Y by
What is the smallest value of \( k \) such that for any polynomial \( f(x) \) of degree $100$ with real coefficients, there exists a polynomial \( g(x) \) of degree at most \( k \) with real coefficients such that the graphs of \( y = f(x) \) and \( y = g(x) \) intersect at exactly $100$ points?
This post has been edited 1 time. Last edited by egxa, Apr 18, 2025, 5:21 PM
Z K Y
The post below has been deleted. Click to close.
This post has been deleted. Click here to see post.
MathLuis
1536 posts
#2
Y by
Recall the well known analysis fact that if a polynomial has exactly $n$ real roots counting multiplicity then its derivative has exactly $n-1$ real roots counting multiplicity. So if $k \le 97$ the considering the $98$-th derivative of $f-g$ gives that for any three given reals $a,b,c$ we must have that $ax^2+bx+c$ always has two real root if $f-g$ had exactly $100$ different roots, thus a contradiction by picking suitable $a,b,c$ (my example would just be $a,c>0$ and $b=0$ lol).
Now we will show $k=98$ works, first clean all the polynomial of degree $98$ inside $f$ using $g$ and from there many a suitable pick, in fact $100$ does not matter so we can prove a slightly stronger claim using induction.
We show that it is possible to construct a polynomial of degree $n$ where only coefficients $x^{n}, x^{n-1}$ are not in our control, so that the polynomial has all real roots with no multiplicity and none of them are zero.
For $n=2$ we can obviously shift the parabola by a constant acording to what is needed due to discriminant criteria so we should be fine here, due to continuity in fact you can just avoid a root being zero or the resulting parabola being tangent to the $x$ axis, for $n=3$ you have something unfree of the form $x^2(ax+b)$ and so you pick some $c(ax+b)+d$ on the free part where $c,d$ have freedom acording to needs like if $b=0$ then $d \ne 0$ and could just be suficiently small given we put $c<0$ to have two roots and that in order to not have repeated roots or the cubic being tangent to the $x$ axis at any moment (continuity yay).
For $n=4$ you basically have control over a depressed cubic upon doing a similar setup as seen above just shift everything by a small constant at the end to satisfy all the given conditions needed and now we will show this is the kind of work you have to do.
Suppose it was true for $n=\ell$ then we prove it for $n=\ell+1$, notice the not free term is $x^{\ell}(ax+b)$ so we just use the free term to focusing on a polynomial of the kind $x^{\ell}+q(x)$ for $\deg q \le \ell-2$, notice here it might happen that $-b \cdot a^{-1}$ is a root twice then we just shift by a very small constant as needed whether is above or below, one of them should work by continuity and IVT, since have $0$ as a root is only a one thing thing on a small interval we can also use continuity to avoid this and still satisfy the no double roots or more condition, hence by using the inductive hypothesis this is also completed and thus our claim is proven.
Just throw the claim and use a suitable $g$ to win, and thus we are done :cool:.
This post has been edited 1 time. Last edited by MathLuis, Apr 19, 2025, 3:49 AM
Z K Y
The post below has been deleted. Click to close.
This post has been deleted. Click here to see post.
iliya8788
8 posts
#3
Y by
We claim that the answer is $\boxed{k=98}$.
Claim 1: $k>97$
Assume the contrary. there exists a polynomial $g(x)$ with degree less than $98$ such that $f(x)-g(x)$ has 100 roots for $f(x)=x^100$. Define $k$ as the degree of $g(x)$
Define $a_{1},...,a_{k}$ such that $f(x)-g(x)=x^{100}+a_{k}x^k+...+a_{0}$. Define $r_{1},...,r_{100}$ as the real roots of $f(x)-g(x)$.
By vieta's formula since the coefficient of $x^{99}$ and $x^{98}$ is equal to $0$: $\sum_{i=1}^{100}r_{i} = 0$ and $\sum_{i<j}^{}r_{i}r_{j} = 0 \implies \sum_{i=1}^{100}r_{i}^2 = 0 \implies r_{i}=0 \implies f(x)-g(x)=0$ which is a contradiction. It follows that $k>97$.
Claim 2: $k=98$
We can basically alter all the coefficients of $f(x)-g(x)$ except the coefficients of $x^{100}$ and $x^{99}$ so by vieta's formula our only restriction is the sum of the roots of the polynomial. So we just need to pick 100 arbitrary pairwise different real numbers such that their sum is equal to $-\frac{a_{99}}{a_{100}}$ with $a_{99}$ being the coefficient of $x^{99}$ and $a_{100}$ being the leading coefficient. Obviously this is possible. From here we just alter the other coefficients so that each one of the coefficients becomes equal to the coefficients of the polynomial that has all these $100$ numbers as roots multiplied by $a_{n}$ and so we are done. $\blacksquare$.
This post has been edited 2 times. Last edited by iliya8788, May 14, 2025, 9:54 AM
Z K Y
N Quick Reply
G
H
=
a