proposition: Lemma scalemx_paste : forall m n1 n2 a (A1 : 'M_(m, n1)) (A2 : 'M_(m, n2)), a *m: pastemx A1 A2 === pastemx (a *m: A1) (a *m: A2).
proof: Proof. by move=> m n1 n2 a A1 A2 i j; rewrite/pastemx/trmx/null_mx/addmx/oppmx/scalemx; case: split; reflexivity. Qed.
imports: ssreflect ssrbool ssrfun eqtype ssrnat seq choice fintype finfun bigops ssralg groups perm zmodp morphisms Ring RingClass bigopsClass Setoid Morphisms