proposition: Lemma drop_polyDMXn n p q : size p <= n -> drop_poly n (p + q * 'X^n) = q.
proof: Proof. by move=> ?; rewrite drop_polyD drop_poly_eq0// drop_polyMXn_id add0r. Qed.
imports: HB(structures) mathcomp(ssreflect ssrbool ssrfun eqtype ssrnat seq choice) mathcomp(fintype bigop finset tuple) mathcomp(div ssralg countalg binomial)