proposition: Lemma lead_coef_lreg c p : GRing.lreg c -> lead_coef (c *: p) = c * lead_coef p.
proof: Proof. by move=> reg_c; rewrite !lead_coefE coefZ lreg_size. Qed.
imports: HB(structures) mathcomp(ssreflect ssrbool ssrfun eqtype ssrnat seq choice) mathcomp(fintype bigop finset tuple) mathcomp(div ssralg countalg binomial)