Анотація:
In this paper we investigate the existence of a positive solution of a second order singular Sturm –
Liouville boundary-value problem, by constructing upper and lower solutions and combined
them with properties of the consequent mapping. Applications to well known Emden – Fowler
and Thomas – Fermi boundary-value problems are also presented. Further we generalize some
of O’Regan’s results, allowing constants in the boundary conditions to be negative.