rw [biUnion_eq_iUnion, M.cl_iUnion_cl_eq_cl_iUnion, biUnion_eq_iUnion]
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
A : Set ι
⊢ M.cl (⋃ i ∈ A, M.cl (Xs i)) = M.cl (⋃ i ∈ A, Xs i)
no goals