MathDB
f(2xy) + f(f(x + y)) = xf(y) + yf(x) + f(x + y)

Source: 21st Philippine Mathematical Olympiad 2019 p1

January 7, 2020
functional equationalgebra

Problem Statement

Find all functions f:R→Rf : R \to R such that f(2xy)+f(f(x+y))=xf(y)+yf(x)+f(x+y)f(2xy) + f(f(x + y)) = xf(y) + yf(x) + f(x + y) for all real numbers xx and yy.