proposition: Lemma size_monicM p q : p \is monic -> q != 0 -> size (p * q) = (size p + size q).-1.
proof: Proof. move/monicP=> mon_p nz_q. by rewrite size_proper_mul // mon_p mul1r lead_coef_eq0. Qed.
imports: HB(structures) mathcomp(ssreflect ssrbool ssrfun eqtype ssrnat seq choice) mathcomp(fintype bigop finset tuple) mathcomp(div ssralg countalg binomial)