MathDB
Function f(f(m)+f(n))=m+n - [Iran Second Round 1988]

Source:

December 7, 2010
functionnumber theory proposednumber theory

Problem Statement

Let f:N→Nf : \mathbb N \to \mathbb N be a function satisfying f(f(m)+f(n))=m+n,   \forall m,n \in \mathbb N. Prove that f(x)=xf(x)=x for all x∈Nx \in \mathbb N.
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