Question 165
Find all functions $f: \mathbb{R} \to \mathbb{R}$, such that
$$
x + f(xf(y)) = f(y) + yf(x)
$$
for all real $x$ and $y$.
$$
x + f(xf(y)) = f(y) + yf(x)
$$
for all real $x$ and $y$.
MathNet 2008-part-03 — 165 problems (EN–VI) Question 165
Math Olympiad Vault · MathNet 2008-part-03 — 165 problems (EN–VI)