MathDB
IMC 2008 Day 1 P1

Source:

July 26, 2014
functionalgebrafunctional equationIMCcollege contests

Problem Statement

Find all continuous functions f:R→Rf: \mathbb{R}\to \mathbb{R} such that f(x)-f(y)\in \mathbb{Q}  \text{ for all }  x-y\in\mathbb{Q}