Question 82
Find all functions $f:\mathbb R\to\mathbb R$ such that for every pair of real numbers $(x,y)$:
$$f(f(x))+f(f(y))=2y+f(x-y).$$
$$f(f(x))+f(f(y))=2y+f(x-y).$$
MathNet 2020 — Math Olympiad Vault — Part 02 Question 82
Math Olympiad Vault · MathNet 2020 — Math Olympiad Vault — Part 02