APMO 2021 P5 - Determine all such functions
- Anindya Biswas
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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 $b$.
"If people do not believe that mathematics is simple, it is only because they do not realize how complicated life is."
— John von Neumann
— John von Neumann