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k a April Highlights and 2025 AoPS Online Class Information
jlacosta   0
Apr 2, 2025
Spring is in full swing and summer is right around the corner, what are your plans? At AoPS Online our schedule has new classes starting now through July, so be sure to keep your skills sharp and be prepared for the Fall school year! Check out the schedule of upcoming classes below.

WOOT early bird pricing is in effect, don’t miss out! If you took MathWOOT Level 2 last year, no worries, it is all new problems this year! Our Worldwide Online Olympiad Training program is for high school level competitors. AoPS designed these courses to help our top students get the deep focus they need to succeed in their specific competition goals. Check out the details at this link for all our WOOT programs in math, computer science, chemistry, and physics.

Looking for summer camps in math and language arts? Be sure to check out the video-based summer camps offered at the Virtual Campus that are 2- to 4-weeks in duration. 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 events:
[list][*]April 3rd (Webinar), 4pm PT/7:00pm ET, Learning with AoPS: Perspectives from a Parent, Math Camp Instructor, and University Professor
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April 9th (Webinar), 4:00pm PT/7:00pm ET, Learn about Video-based Summer Camps at the Virtual Campus
[*]April 10th (Math Jam), 4:30pm PT/7:30pm ET, 2025 MathILy and MathILy-Er Math Jam: Multibackwards Numbers
[*]April 22nd (Webinar), 4:00pm PT/7:00pm ET, Competitive Programming at AoPS (USACO).[/list]
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0 replies
jlacosta
Apr 2, 2025
0 replies
Integration Bee Kaizo
Calcul8er   51
N an hour ago by BaidenMan
Hey integration fans. I decided to collate some of my favourite and most evil integrals I've written into one big integration bee problem set. I've been entering integration bees since 2017 and I've been really getting hands on with the writing side of things over the last couple of years. I hope you'll enjoy!
51 replies
Calcul8er
Mar 2, 2025
BaidenMan
an hour ago
Equation over a finite field
loup blanc   0
3 hours ago
Find the set of $x\in\mathbb{F}_{5^5}$ such that the equation in the unknown $y\in \mathbb{F}_{5^5}$:
$x^3y+y^3+x=0$ admits $3$ roots: $a,a,b$ s.t. $a\not=b$.
0 replies
loup blanc
3 hours ago
0 replies
interesting integral
Martin.s   1
N Today at 2:46 PM by ysharifi
$$\int_0^\infty \frac{\sinh(t)}{t \cosh^3(t)} dt$$
1 reply
Martin.s
Yesterday at 3:12 PM
ysharifi
Today at 2:46 PM
Two times derivable real function
Valentin Vornicu   10
N Today at 2:04 PM by Rohit-2006
Source: RMO 2008, 11th Grade, Problem 3
Let $ f: \mathbb R \to \mathbb R$ be a function, two times derivable on $ \mathbb R$ for which there exist $ c\in\mathbb R$ such that
\[ \frac { f(b)-f(a) }{b-a} \neq f'(c) ,\] for all $ a\neq b \in \mathbb R$.

Prove that $ f''(c)=0$.
10 replies
Valentin Vornicu
Apr 30, 2008
Rohit-2006
Today at 2:04 PM
No more topics!
complex roots of polynomial and inequality for coefficients
su7e   5
N May 17, 2021 by XbenX
polynomial $P(z)=a_nz^n+\dots+ a_1z+a_0\in\mathbb{R}[x]$, $\deg P=n\ge 3$, has all complex roots in a set $\{z\in\mathbb{C}: \mbox{Re}\,z<0\}$.
show that $a_ka_{k+3}<a_{k+1}a_{k+2}$ for $k=0,1,\dots, n-3$.
5 replies
su7e
Nov 29, 2012
XbenX
May 17, 2021
complex roots of polynomial and inequality for coefficients
G H J
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su7e
16 posts
#1 • 2 Y
Y by Adventure10, Mango247
polynomial $P(z)=a_nz^n+\dots+ a_1z+a_0\in\mathbb{R}[x]$, $\deg P=n\ge 3$, has all complex roots in a set $\{z\in\mathbb{C}: \mbox{Re}\,z<0\}$.
show that $a_ka_{k+3}<a_{k+1}a_{k+2}$ for $k=0,1,\dots, n-3$.
Z K Y
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CJA
155 posts
#2 • 2 Y
Y by Adventure10, Mango247
any ideas?
Z K Y
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GreenKeeper
1688 posts
#3 • 1 Y
Y by Adventure10
It's probably related to Routh-Hurwitz theorem.

https://en.wikipedia.org/wiki/Hurwitz_matrix
Z K Y
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CJA
155 posts
#4 • 1 Y
Y by Adventure10
GreenKeeper wrote:
It's probably related to Routh-Hurwitz theorem.

https://en.wikipedia.org/wiki/Hurwitz_matrix

thank you,this problem is really related to Routh-Hurwitz theorem,it is about Hurwitz polynomial,and I know the problem is called xie xvkai stability criterion(proposed in 1963) now.
Z K Y
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Xiaolin
36 posts
#6
Y by
Any solutions?
Z K Y
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XbenX
590 posts
#7 • 1 Y
Y by GreenKeeper
It is IMC 2003 P6; you can find a solution on the official page.
Z K Y
N Quick Reply
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