proposition: Lemma Fadjoin_sub E x y : x \in <<E; y>>%VS -> (<<E; x>> <= <<E; y>>)%VS.
proof: Proof. by move=> xEy; apply/FadjoinP; rewrite subv_adjoin. Qed.
imports: HB(structures) mathcomp(all_ssreflect all_fingroup all_algebra) mathcomp(all_solvable all_field) Abel(various char0)