Upper and Lower Solutions for Higher Order Boundary Value Problems

This paper is concerned with the study of the higher order boundary value problem 8> >: u(t) = f(t; u(t); u(t); :::; u (t)); n 2; u(0) = 0; i = 0; :::; n 3; a u (0) b u (0) = A; c u (1) + d u (1) = B; with f : [0; 1] R ! R a continuous function, a; c; A;B 2 R and b; d 0 such that a + b > 0 and c + d > 0: It is assumed that lower and upper solutions exist and that f satis…es Nagumotype conditions. An existence result is obtained