proposition: Lemma mul_mx_scalar m n a (A : 'M[R]_(m, n)) : A *m a%:M = a *: A.
proof: Proof. by rewrite scalar_mxC mul_scalar_mx. 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 countalg finalg zmodp)