摘要

We investigate the existence of positive solutions for the boundary value problem
u((n)) (t) + f (t, u (t), u' (t),..., u((n-2)) (t), u((n-1)) (t)) = 0, 0 < t < 1,
u(0) = u'(0) = ... = u((n-2)) (0) = 0, u((n-1)) (1) = Sigma (m-2)(i-1) k(i)u((n-1)) (xi(i)),
where f : [0, 1] x (R+)(n) -> R+ is continuous, k(i) > 0 (i = 1, 2,..., m - 2), 0 < Sigma(m-2)(i=1) k(i) < 1. We give at first the associated Green's function and some of its properties. Then, imposing growth conditions on f, we obtain the existence of at least three positive solutions for the boundary value problem by using the five-functional-fixed-point theorem. Finally, we give an example to demonstrate our result.