A U B = N (combinatorics)
Source: Federation of Bosnia, 1. Grades 2008.
April 23, 2008
Problem Statement
Given are two disjoint sets and such that their union is . Prove that for all positive integers there exist different numbers and , both greater than , such that either \{ a,b,a \plus{} b \} is contained in or \{ a,b,a \plus{} b \} is contained in .