proposition: Lemma scalerBl a b v : (a - b) *: v = a *: v - b *: v.
proof: Proof. by rewrite scalerDl scaleNr. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat div seq) mathcomp(choice fintype finfun bigop prime binomial)