proposition: Lemma memv_ker f v : (v \in lker f) = (f v == 0).
proof: Proof. by rewrite -memv0 !memvE subv0 lkerE limg_line. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq choice) mathcomp(fintype bigop finfun tuple) mathcomp(ssralg matrix mxalgebra zmodp)