proposition: Lemma root_comp p q x : root (p \Po q) x = root p (q.[x]).
proof: Proof. by rewrite !rootE horner_comp. Qed.
imports: HB(structures) mathcomp(ssreflect ssrbool ssrfun eqtype ssrnat seq choice) mathcomp(fintype bigop finset tuple) mathcomp(div ssralg countalg binomial)