proposition: Lemma geigenspaceE n' (g : 'M_n'.+1) a : geigenspace g a = kermx ((g - a%:M) ^+ n'.+1).
proof: Proof. by rewrite /geigenspace /kermxpoly rmorphXn/= rmorphB/= horner_mx_X horner_mx_C. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat choice seq) mathcomp(div fintype tuple finfun bigop fingroup perm) mathcomp(ssralg zmodp matrix mxalgebra poly polydiv)