Title: Rootfinding and approximation approaches through neural networks Authors: Michael G. Epitropakis, Michael N. Vrahatis, University of Patras Abstract: Two important scientific problems that arise in a huge variety of applications are the approximation of Multivariate High Order Polynomials, as well as, the estimation of roots of High Order Univariate Polynomials. Among the various proposed approaches for these problems Artificial Neural Networks have recently demonstrated their ability to provide accurate and fast approximations and root estimations. In this contribution we employ High Order Neural Networks, and specifically Ridge Polynomial Networks for the approximation of multivariate polynomial equations. We recommend the use of stochastic global optimization techniques, like Differential Evolution and Particle Swarm Optimization for the learning process to obtain better solutions. We further propose a two step technique for the estimation of a number of arbitrary roots of higher order polynomials. This technique at a first step considers a trained Feedforward Neural Network as an oracle, that returns the number of real roots of a univariate polynomial. At the next step this information is used by a known High Order Neural Network root-finder to provide the final roots estimation.