proposition: Lemma dernr x : x \in `]a, b] -> p.[x] < p.[a].
proof: Proof. move=> axb; rewrite gtr_horner ?(itvP axb) //. by apply: subitvPl axb; rewrite bound_lexx. Qed.
imports: mathcomp.ssreflect.ssreflect mathcomp(ssrfun ssrbool eqtype ssrnat seq choice fintype) mathcomp(bigop order ssralg poly polydiv ssrnum zmodp) mathcomp(polyorder path interval ssrint)