Question 41
Find all functions $f : \mathbb{R}^+ \to \mathbb{R}^+$ such that
$$
(x + y)f(2yf(x) + f(y)) = x^3 f(yf(x)), \quad \forall x, y \in \mathbb{R}^+.
$$
$$
(x + y)f(2yf(x) + f(y)) = x^3 f(yf(x)), \quad \forall x, y \in \mathbb{R}^+.
$$
MathNet 2015-part-01 — 191 problems (EN–VI) Question 41
Math Olympiad Vault · MathNet 2015-part-01 — 191 problems (EN–VI)