MathDB
Monic polynomial with two high zero coefficients

Source: Polish Second Round 2001

March 6, 2012
algebrapolynomialalgebra proposed

Problem Statement

Let n3n\ge 3 be a positive integer. Prove that a polynomial of the form xn+an3xn3+an4xn4++a1x+a0,x^n+a_{n-3}x^{n-3}+a_{n-4}x^{n-4}+\ldots +a_1x+a_0, where at least one of the real coefficients a0,a1,,an3a_0,a_1,\ldots ,a_{n-3} is nonzero, cannot have all real roots.