Positive solutions of boundary value problems for nonlinear differential equations

Sufficient conditions for the existence of a positive solution of two-point boundary value problem for a nonlinear ordinary differential equation of the fourth order were improved. The new sufficient conditions for the existence and uniqueness of the positive solution of two-point boundary value problem for a special kind of nonlinear ordinary differential equation with fractional derivatives of order $\alpha$ were obtained. The new sufficient conditions for the existence and uniqueness of positive radially symmetric solution of the Dirichlet problem for a system of nonlinear differential equations with $p$-laplacian were obtained.