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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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Find all p(x) such that p(p) is a power of 2
truongphatt2668   5
N 2 hours ago by tom-nowy
Source: ???
Find all polynomial $P(x) \in \mathbb{R}[x]$ such that:
$$P(p_i) = 2^{a_i}$$with $p_i$ is an $i$ th prime and $a_i$ is an arbitrary positive integer.
5 replies
1 viewing
truongphatt2668
Thursday at 1:05 PM
tom-nowy
2 hours ago
Interesting problem from a friend
v4913   10
N 2 hours ago by OronSH
Source: I'm not sure...
Let the incircle $(I)$ of $\triangle{ABC}$ touch $BC$ at $D$, $ID \cap (I) = K$, let $\ell$ denote the line tangent to $(I)$ through $K$. Define $E, F \in \ell$ such that $\angle{EIF} = 90^{\circ}, EI, FI \cap (AEF) = E', F'$. Prove that the circumcenter $O$ of $\triangle{ABC}$ lies on $E'F'$.
10 replies
v4913
Nov 25, 2023
OronSH
2 hours ago
IMO ShortList 2002, algebra problem 3
orl   25
N 3 hours ago by Mathandski
Source: IMO ShortList 2002, algebra problem 3
Let $P$ be a cubic polynomial given by $P(x)=ax^3+bx^2+cx+d$, where $a,b,c,d$ are integers and $a\ne0$. Suppose that $xP(x)=yP(y)$ for infinitely many pairs $x,y$ of integers with $x\ne y$. Prove that the equation $P(x)=0$ has an integer root.
25 replies
1 viewing
orl
Sep 28, 2004
Mathandski
3 hours ago
Inequality on APMO P5
Jalil_Huseynov   41
N 3 hours ago by Mathandski
Source: APMO 2022 P5
Let $a,b,c,d$ be real numbers such that $a^2+b^2+c^2+d^2=1$. Determine the minimum value of $(a-b)(b-c)(c-d)(d-a)$ and determine all values of $(a,b,c,d)$ such that the minimum value is achived.
41 replies
Jalil_Huseynov
May 17, 2022
Mathandski
3 hours ago
APMO 2016: one-way flights between cities
shinichiman   18
N 3 hours ago by Mathandski
Source: APMO 2016, problem 4
The country Dreamland consists of $2016$ cities. The airline Starways wants to establish some one-way flights between pairs of cities in such a way that each city has exactly one flight out of it. Find the smallest positive integer $k$ such that no matter how Starways establishes its flights, the cities can always be partitioned into $k$ groups so that from any city it is not possible to reach another city in the same group by using at most $28$ flights.

Warut Suksompong, Thailand
18 replies
shinichiman
May 16, 2016
Mathandski
3 hours ago
Circles intersecting each other
rkm0959   9
N 3 hours ago by Mathandski
Source: 2015 Final Korean Mathematical Olympiad Day 2 Problem 6
There are $2015$ distinct circles in a plane, with radius $1$.
Prove that you can select $27$ circles, which form a set $C$, which satisfy the following.

For two arbitrary circles in $C$, they intersect with each other or
For two arbitrary circles in $C$, they don't intersect with each other.
9 replies
rkm0959
Mar 22, 2015
Mathandski
3 hours ago
Max value
Hip1zzzil   0
3 hours ago
Source: KMO 2025 Round 1 P12
Three distinct nonzero real numbers $x,y,z$ satisfy:

(i)$2x+2y+2z=3$
(ii)$\frac{1}{xz}+\frac{x-y}{y-z}=\frac{1}{yz}+\frac{y-z}{z-x}=\frac{1}{xy}+\frac{z-x}{x-y}$
Find the maximum value of $18x+12y+6z$.
0 replies
Hip1zzzil
3 hours ago
0 replies
2018 Hong Kong TST2 problem 4
YanYau   4
N 3 hours ago by Mathandski
Source: 2018HKTST2P4
In triangle $ABC$ with incentre $I$, let $M_A,M_B$ and $M_C$ by the midpoints of $BC, CA$ and $AB$ respectively, and $H_A,H_B$ and $H_C$ be the feet of the altitudes from $A,B$ and $C$ to the respective sides. Denote by $\ell_b$ the line being tangent tot he circumcircle of triangle $ABC$ and passing through $B$, and denote by $\ell_b'$ the reflection of $\ell_b$ in $BI$. Let $P_B$ by the intersection of $M_AM_C$ and $\ell_b$, and let $Q_B$ be the intersection of $H_AH_C$ and $\ell_b'$. Defined $\ell_c,\ell_c',P_C,Q_C$ analogously. If $R$ is the intersection of $P_BQ_B$ and $P_CQ_C$, prove that $RB=RC$.
4 replies
YanYau
Oct 21, 2017
Mathandski
3 hours ago
Prove that the triangle is isosceles.
TUAN2k8   4
N 3 hours ago by JARP091
Source: My book
Given acute triangle $ABC$ with two altitudes $CF$ and $BE$.Let $D$ be the point on the line $CF$ such that $DB \perp BC$.The lines $AD$ and $EF$ intersect at point $X$, and $Y$ is the point on segment $BX$ such that $CY \perp BY$.Suppose that $CF$ bisects $BE$.Prove that triangle $ACY$ is isosceles.
4 replies
TUAN2k8
Yesterday at 9:55 AM
JARP091
3 hours ago
Pythagoras...
Hip1zzzil   0
3 hours ago
Source: KMO 2025 Round 1 P20
Find the sum of all $k$s such that:
There exists two odd positive integers $a,b$ such that ${k}^{2}={a}^{2b}+{(2b)}^{4}.$
0 replies
Hip1zzzil
3 hours ago
0 replies
a