MathDB
Tuymaada 2010, Junior League, Problem 5

Source:

July 18, 2010
limitcalculusintegrationalgebra unsolvedalgebra

Problem Statement

We have a set MM of real numbers with M>1|M|>1 such that for any xMx\in M we have either 3x2M3x-2\in M or 4x+5M-4x+5\in M. Show that MM is infinite.