Abstract. The Newton-Kantorovich hypothesis (15) has been used for a long time as a sufficient condition for convergence of Newton's method to a locally unique solution of a nonlinear equation in a Banach space setting. Recently in [3], [4] we showed that this hypothesis can always be replaced by a condition weaker in general (see (18), (19) or (20)) whose verification requires the same computational cost. Moreover, finer error bounds and at least as precise information on the location of the solution can be obtained this way. Here we show that we can further weaken conditions (18)- (20) A large number of problems in applied mathematics and also in engineering are solved by finding solutions of certain equations. For example, dynamical systems are mathematically modeled by difference or differential equations, and their solutions usually represent states of the systems. For the sake of simplicity, assume that a time-invariant system is driven by the equationẋ = G(x) (for some suitable operator G), where x is the state. Then the equilibrium states are determined by solving equation (1). Similar equations are used in the case of discrete systems. The unknowns of engineering equations can be functions (difference, differential, and integral equations), 2000 Mathematics Subject Classification: 65H10, 65G99, 47H17, 49M15.