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(1+a^2)(1+b^2)(1+c^2) is perfect square-[UKRMO 2009 Grade 8]

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January 21, 2011

Problem Statement

Let a,b,ca, b, c be integers satisfying ab+bc+ca=1.ab + bc + ca = 1. Prove that (1+a2)(1+b2)(1+c2)(1+ a^2 )(1+ b^2 )(1+ c^2 ) is a perfect square.