Question 179
Find all functions $f: \mathbb{R} \to \mathbb{R}$ such that
$$
4f(x+f(y)) = f(x)+f(y)+f(xy)+1
$$
for all real numbers $x, y$.
$$
4f(x+f(y)) = f(x)+f(y)+f(xy)+1
$$
for all real numbers $x, y$.
MathNet 2015-part-06 — 191 problems (EN–VI) Question 179
Math Olympiad Vault · MathNet 2015-part-06 — 191 problems (EN–VI)