2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/208607This is an introduction to the theory of disconjugacy for a second order linear differential equation. We give new proofs of some of basic results and obtain new sufficient conditions for disconjugacy (in particular, on the whole real axis).Classical Analysis and ODEsDynamical Systems34B05; 35B40text