exact M.cl_subset_cl fun e he ↦ (h.basis_subset (subset_insert _ _) (insert_subset he h.subset))
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
h : M.Basis I X
⊢ M.cl X ⊆ M.cl {x | M.Basis I (insert x I)}
no goals