Theorem: Matroid.contract_minor (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 : Set α
M₀ M₁ M₂ M : Matroid α
C : Set α
⊢ M ／ C ≤m M
Tactic:
rw [← (M ／ C).delete_empty]
State after:
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 : Set α
⊢ M ／ C ＼ ∅ ≤m M

State before:
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 : Set α
⊢ M ／ C ＼ ∅ ≤m M
Tactic:
apply contract_delete_minor
State after:
no goals