Theorem: Matroid.contract_contract_diff (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
C₁ C₂ : Set α
⊢ M ／ C₁ ／ C₂ = M ／ C₁ ／ (C₂ \ C₁)
Tactic:
simp
State after:
no goals