proposition: Lemma rootP p x : reflect (p.[x] = 0) (root p x).
proof: Proof. exact: eqP. Qed.
imports: HB(structures) mathcomp(ssreflect ssrbool ssrfun eqtype ssrnat seq choice) mathcomp(fintype bigop finset tuple) mathcomp(div ssralg countalg binomial)