Question 117
Determine all the real-valued functions $f$ defined on the real line, which satisfies for all real numbers $x$ and $y$
$$
f(x+y)f(f(x)-y) = xf(x) - yf(y).
$$
$$
f(x+y)f(f(x)-y) = xf(x) - yf(y).
$$
MathNet 2008-part-02 — 165 problems (EN–VI) Question 117
Math Olympiad Vault · MathNet 2008-part-02 — 165 problems (EN–VI)