proposition: Lemma kerAK p m n (M : 'M_(m,n)) (N : 'M[R]_(p, _)) : N *m ker M *m M = 0.
proof: Proof. by rewrite -mulmxA kerK mulmx0. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat div seq path) mathcomp(ssralg fintype perm choice matrix bigop zmodp mxalgebra poly) ssrcomplements dvdring stronglydiscrete