Problem

Source: IMO Shortlist 1992, Problem 19

Tags: algebra, polynomial, number theory, coefficients, Divisibility, IMO Shortlist



Let $ f(x) = x^8 + 4x^6 + 2x^4 + 28x^2 + 1.$ Let $ p > 3$ be a prime and suppose there exists an integer $ z$ such that $ p$ divides $ f(z).$ Prove that there exist integers $ z_1, z_2, \ldots, z_8$ such that if \[ g(x) = (x - z_1)(x - z_2) \cdot \ldots \cdot (x - z_8),\] then all coefficients of $ f(x) - g(x)$ are divisible by $ p.$