proposition: Lemma coefB p q i : (p - q)`_i = p`_i - q`_i.
proof: Proof. by rewrite coefD coefN. Qed.
imports: HB(structures) mathcomp(ssreflect ssrbool ssrfun eqtype ssrnat seq choice) mathcomp(fintype bigop finset tuple) mathcomp(div ssralg countalg binomial)