simp [hI, show ¬ M.Indep (insert e I) from fun h ↦ hI <| h.subset <| subset_insert _ _]
case neg
α : Type u_1
ι : Type u_2
M : Matroid α
F I J X Y B C R : Set α
e f x y : α
hI : ¬M.Indep I
⊢ M.Indep (insert e I) ↔ M.Indep I ∧ (e ∉ I → e ∈ M.E \ M.cl I)
no goals