MathDB
Complex polynomials

Source: Miklos Schweitzer 2023, Problem 8

March 7, 2024
complex analysispolynomial

Problem Statement

Let qq{} be an arbitrary polynomial with complex coefficients which is not identically 00 and Γq={z:q(z)=1}\Gamma_q =\{z : |q(z)| = 1\} be its contour line. Prove that for every point z0Γqz_0\in\Gamma_q there is a polynomial pp{} for which p(z0)=1|p(z_0)| = 1 and p(z)<1|p(z)|<1 for any zΓq{z0}.z\in\Gamma_q\setminus\{z_0\}.