2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/71004We show that there exist non-formal compact oriented manifolds of dimension $n$ and with first Betti number $b_1=b\geq 0$ if and only if $n\geq 3$ and $b\geq 2$, or $n\geq (7-2b)$ and $0\leq b\leq 2$. Moreover, we present explicit examples for each one of these cases.8 pages, one reference updatedDifferential GeometryAlgebraic Topology55S30; 55P62text