2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/63811We prove that, if μ<\lfloor n/2\rfloor, then every rational plane curve of degree n and class μis a limit of parametrizations of the same degree and class μ+1. This property was conjectured in D.Cox, T.Sederberg,F.Chen's paper: "The moving line ideal basis of planar rational curves" (Comput. Aided Geom. Des. 15 (1998), 803-827), and its validity allows an explicit description of the variety of parametrizations of degree n and class μ, for all (n,μ).6 pages, revised version accepted for publication in Communications in AlgebraAlgebraic GeometryCommutative Algebra13Pxx, 14H50text