A Generalization of Obreshkoff-Ehrlich Method for Multiple Roots of Polynomial Equations

In this paper we develop a new method which is a generalization of the Obreshkoff -Ehrlich method for the cases of algebraic, trigonometric and exponential polynomials. This method has a cubic rate of convergence. It is efficient from the computational point of view and can be used for simultaneous finding all roots if the roots have known multiplicities. This new method in spite of the arbitrariness of multiplicities is of the same complexity as the methods for simultaneous finding all roots of simple roots. We do not use divided differences with multiple knots and this fact does not lead to calculation of derivatives of the given polynomial of higher order, but only of first ones.