Journal of Applied Mathematics and Computing https://doi.org/10.1007/s12190-019-01285-8 ORIGINAL RESEARCH Successive iteration technique for singular nonlinear system with four-point boundary conditions Amit K. Barnwal 1 · Priti Pathak 1 Received: 18 June 2019 © Korean Society for Informatics and Computational Applied Mathematics 2019 Abstract In this paper, the existence of at least one positive solution of the system of singular differential equations with four-point coupled boundary conditions is discussed. A constructive monotonic iterative technique on the equivalent completely continuous nonlinear operator is used to establish the result. This method produces an approximate solution in the form of series which is very helpful in developing a numerical scheme for the positive solution of the system. It is demonstrated through the examples. Keywords Positive solution · Coupled singular boundary value problems · Monotonic iterative technique · Coupled boundary conditions Mathematics Subject Classification 34B15 · 34B16 · 34B18 1 Introduction We aim in this work to discuss the existence of positive solution (PS) for the following singular nonlinear system of differential equations with four-point coupled boundary conditions (BCs) ( py ) = qf 1 (t , y , z ), t (0, 1), ( pz ) = qf 2 (t , y , z ), t (0, 1), y (0) = z (0) = 0, y (1) = μ 1 z 1 ), z (1) = μ 2 y 2 ). (1) Here parameters μ 1 1 2 and ν 2 satisfy 0 1 μ 2 h 1 )h 2 )< h (1) 2 , h (t ) = t 0 1 p(x ) dx and ν 1 2 (0, 1). Boundary value problems (BVPs) (1) is singular in B Amit K. Barnwal amit.bhu1@gmail.com Priti Pathak pritiipathak@gmail.com 1 Department of Mathematics and Scientific Computing, MMM University of Technology, Gorakhpur 273010, India 123