2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/150006Generalizing a classical lemma of Castelnuovo, we characterize rational normal curves (resp. linearly normal elliptic curves) as curves $C\subset \PP^n$ such that the number of linearly independent hypersurfaces $Z\supset C$ of given degree~$m$ is maximal (resp. next to maximal).14 pages, no figures, AMSTeX v 2.1 with amspptAlgebraic Geometry14H50text