rw [← loopyOn_dual_eq, ← contract_dual_eq_dual_delete, loopyOn_contract, loopyOn_dual_eq]
α : Type u_1
M M' N : Matroid α
e f : α
I J R B X✝ Y Z K E✝ E X : Set α
⊢ freeOn E ＼ X = freeOn (E \ X)
no goals