Theorem: Matroid.dual_contract_dual_eq_delete (Matroid/Minor/Basic.lean)

State before:
α : Type u_1
M✝ M' N : Matroid α
e f : α
I J R B X✝ Y Z K C C₁ C₂ : Set α
M : Matroid α
X : Set α
⊢ (M✶ ／ X)✶ = M ＼ X
Tactic:
rw [← dual_delete_dual_eq_contract, dual_dual, dual_dual]
State after:
no goals