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Polynomial is a square of a polynomial

Source: 51 Polish MO 2000 Second Round - Problem 6

April 23, 2018
algebrapolynomialSquaresPoland

Problem Statement

Polynomial w(x)w(x) of second degree with integer coefficients takes for integer arguments values, which are squares of integers. Prove that polynomial w(x)w(x) is a square of a polynomial.