f(xf(x+y))+f((x+y)f(y))=(x+y)^2
Source: 2021 Ukraine NMO 11.4
April 2, 2021
functional equationfunctionalalgebra
Problem Statement
Find all the following functions , which for arbitrary valid holds equality:
(Vadym Koval)
Source: 2021 Ukraine NMO 11.4