New posts in Contest Math

CGMO 2020: Prove that $X, P, Q, Y$ are concyclic.

number of solutions of $f(f(f(f(x))))$

Prove that $-\sqrt{c}<ab<0$ if $a^4-2019a=b^4-2019b=c$.

(BAMO $2013/3$) $ABH$, $BCH$ and $CAH$ is congruent to $ABC$.

Find the last two digits of $7^{100}-3^{100}$

Book recommendation : Olympiad Combinatorics book

Polynomial olympiad problem

USA TST 2018/P1: Prove that the $n^{\text{th}}$ smallest positive integer relatively prime to $n$ is at least $\sigma(n)$

why $\left(\left( \left(-\frac{1}{4}\right)^{-2}\right)^\frac{1}{4}\right) \neq \left(\left(-\frac{1}{4}\right)^{-\frac{1}{2}}\right)$?

How do I find integers $x,y,z$ such that $x+y=1-z$ and $x^3+y^3=1-z^2$?