MathDB
Romania District Olympiad 2010

Source: Grade IX

March 13, 2010
floor functionalgebra proposedalgebra

Problem Statement

For any real number x x prove that: x\in \mathbb{Z}\Leftrightarrow \lfloor x\rfloor \plus{}\lfloor 2x\rfloor\plus{}\lfloor 3x\rfloor\plus{}...\plus{}\lfloor nx\rfloor\equal{}\frac{n(\lfloor x\rfloor\plus{}\lfloor nx\rfloor)}{2}\ ,\ (\forall)n\in \mathbb{N}^*