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