proposition: Lemma prev_root_lt p a b : a < b -> p != 0 -> prev_root p a b < b.
proof: Proof. move=> ab np0; case: prev_rootP=> [p0|y _ py0 hy _|c _ -> _]. * by rewrite p0 eqxx in np0. * by rewrite (itvP hy). * by rewrite lt_minl ab. 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)