Question 24
Find all functions $f : \mathbb{R} \to \mathbb{R}$ such that for any $x, y \in \mathbb{R}$,
$$ f(xf(y) + y^{2021}) = yf(x) + (f(y))^{2021}. $$
(Contributed by Fu Yunhao)
$$ f(xf(y) + y^{2021}) = yf(x) + (f(y))^{2021}. $$
(Contributed by Fu Yunhao)