2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/95186Given a Banach space. We show that its three times dual space can be written as a direct sum. Then being one of the sumands null is a necessary and sufficient condition for the dual space to be reflexive. We end with an application of this result to the known relationship between the reflexivity of a Banach space and that of its dual space.3 pages. Minor gramatical changeFunctional Analysistext