proposition: Lemma closed_nonrootP p : reflect (exists x, ~~ root p x) (p != 0).
proof: Proof. exact: PreClosedField.closed_nonrootP. Qed.
imports: HB(structures) mathcomp(ssreflect ssrbool ssrfun eqtype ssrnat seq choice) mathcomp(fintype bigop finset tuple) mathcomp(div ssralg countalg binomial)