rw [contract_delete_diff, contract_delete_comm _ disjoint_sdiff_right]
α : Type u_1
M✝ M' N : Matroid α
e f : α
I J R B X Y Z K : Set α
M₀ M₁ M₂ M : Matroid α
C D : Set α
⊢ M ／ C ＼ D = M ＼ (D \ C) ／ C
no goals