proposition: Lemma scalemxAr a A B : a *: (A *m B) = A *m (a *: B).
proof: Proof. by apply: trmx_inj; rewrite trmx_mul !linearZ /= trmx_mul scalemxAl. 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)