2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/113616The dynamical evolution of the scale factor of FRW cosmological model is presented, when the equation of state of the material content assume the form $\rm p=γρ$, $\rm γ=constant$, including the cosmological term. We use the WKB approximation and the relation with the Einstein-Hamilton-Jacobi equation to obtain the exact solutions.work presented in the IV Mexican workshop, 2004 Morelia MichoacanGeneral Relativity and Quantum Cosmologytext