2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/156917We give an effective method for controlling the maximum number of limit cycles of some planar polynomial systems. It is based on a suitable choice of a Dulac function and the application of the well-known Bendixson-Dulac Criterion for multiple connected regions. The key point is a new approach to control the sign of the functions involved in the criterion. The method is applied to several examples.14 pages, O figuresDynamical SystemsClassical Analysis and ODEs34C05; 34C07text