Abstract: | We study the existence of positive solutions of the equation f(x, y(x),y(x)) =0 with either y(0)= y(1) =y(0) = y(1) =0 or y(0) = y'(1)=y(0) = y(1) = 0. We show the existence of at least one positive solution if f is either superlinear of sublinear by a simple application of a fixed point theorem In cones. |