proposition: Lemma deg2_poly_lt0r x : r2 < x -> p.[x] < 0.
proof: Proof. by move=> ?; rewrite -oppr_gt0 -hornerN deg2_poly_gt0r// deltaN r2N. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq choice) mathcomp(ssrAC div fintype path bigop order finset fingroup) mathcomp(ssralg poly)