Question 67
Find all functions $f: \mathbb{R} \to [-2019, 2019]$ for which
$$
2f(f(x)) + f(f(-x)) + 8f(x) + 4f(-x) + 4x = 0
$$
for all real numbers $x$.
$$
2f(f(x)) + f(f(-x)) + 8f(x) + 4f(-x) + 4x = 0
$$
for all real numbers $x$.
MathNet 2019-part-01 — 184 problems (EN–VI) Question 67
Math Olympiad Vault · MathNet 2019-part-01 — 184 problems (EN–VI)