MathDB
f(x)^2=f(x sqrt(2))

Source: Brazilian Undergrad MO 2021 Problem 2

May 12, 2022
functionsreal analysisfunctionBrazilian Undergrad MO 2021

Problem Statement

Find all functions f:RRf: \mathbb{R} \rightarrow \mathbb{R} from C2C^2 (id est, ff is twice differentiable and ff'' is continuous.) such that for every real number tt we have f(t)2=f(t2)f(t)^2=f(t \sqrt{2}).