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