proposition: Lemma algebraic_sub x y : algebraicOver FtoE x -> algebraicOver FtoE y -> algebraicOver FtoE (x - y).
proof: Proof. by move=> algFx /algebraic_opp; apply: algebraic_add. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat choice seq) mathcomp(div fintype tuple finfun bigop fingroup perm) mathcomp(ssralg zmodp matrix mxalgebra poly polydiv)