proposition: Lemma take_polyDMXn n p q : size p <= n -> take_poly n (p + q * 'X^n) = p.
proof: Proof. by move=> ?; rewrite take_polyD take_poly_id// take_polyMXn_0 addr0. Qed.
imports: HB(structures) mathcomp(ssreflect ssrbool ssrfun eqtype ssrnat seq choice) mathcomp(fintype bigop finset tuple) mathcomp(div ssralg countalg binomial)