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2a^4+2b^4+2c^4 square if a+b+c=0

Source: Moldova 2000 Grade 9 P2

April 25, 2021
number theory

Problem Statement

Prove that if a,b,c are integers with a+b+c=0a+b+c=0, then 2a4+2b4+2c42a^4+2b^4+2c^4 is a perfect square.