APMO 2021 P5 - Determine all such functions

Discussion on Asian Pacific Mathematical Olympiad (APMO)
Anindya Biswas
Posts: 255
Joined: Fri Oct 02, 2020 8:51 pm
Determine all functions $f:\mathbb{Z}\to\mathbb{Z}$ such that $f(f(a)-b)+bf(2a)$ is a perfect square for all integers $a$ and $b$.