proposition: Lemma lead_coefMX p : lead_coef (p * 'X) = lead_coef p.
proof: Proof. have [-> | nzp] := eqVneq p 0; first by rewrite mul0r. by rewrite /lead_coef !nth_last polyseqMX. Qed.
imports: HB(structures) mathcomp(ssreflect ssrbool ssrfun eqtype ssrnat seq choice) mathcomp(fintype bigop finset tuple) mathcomp(div ssralg countalg binomial)