proposition: Lemma submx0null m1 m2 n (A : 'M[F]_(m1, n)) : (A <= (0 : 'M_(m2, n)))%MS -> A = 0.
proof: Proof. by case/submxP=> D; rewrite mulmx0. Qed.
imports: HB(structures) mathcomp(ssreflect ssrbool ssrfun eqtype ssrnat seq choice) mathcomp(fintype finfun bigop finset fingroup perm order) mathcomp(div prime binomial ssralg finalg zmodp matrix)