rw [← cl_inter_ground, iUnion_inter]
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
M : Matroid α
Xs : ι → Set α
⊢ M.cl (⋃ i, Xs i) ⊆ M.cl (⋃ i, M.cl (Xs i))
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
M : Matroid α
Xs : ι → Set α
⊢ M.cl (⋃ i, Xs i ∩ M.E) ⊆ M.cl (⋃ i, M.cl (Xs i))