proposition: Lemma mulmx1_min_rank r m n (A : 'M_(m, n)) M N : M *m A *m N = 1%:M :> 'M_r -> r <= \rank A.
proof: Proof. by rewrite -{1}(mulmx_base A) mulmxA -mulmxA; move/mulmx1_min. 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)