Theorem: Matroid.delete_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 D D₁✝ D₂✝ R : Set α
M : Matroid α
D₁ D₂ : Set α
⊢ M ＼ D₁ ＼ D₂ = M ＼ (D₁ ∪ D₂)
Tactic:
rw [← restrict_compl, ← restrict_compl, ← restrict_compl, restrict_restrict_eq,
  restrict_ground_eq, diff_diff]
State after:
case hR
α : Type u_1
M✝ M' N : Matroid α
e f : α
I J R✝ B X Y Z K D D₁✝ D₂✝ R : Set α
M : Matroid α
D₁ D₂ : Set α
⊢ (M ↾ M.E \ D₁).E \ D₂ ⊆ M.E \ D₁

State before:
case hR
α : Type u_1
M✝ M' N : Matroid α
e f : α
I J R✝ B X Y Z K D D₁✝ D₂✝ R : Set α
M : Matroid α
D₁ D₂ : Set α
⊢ (M ↾ M.E \ D₁).E \ D₂ ⊆ M.E \ D₁
Tactic:
simp [diff_subset]
State after:
no goals