Theorem: Matroid.delete_er_eq (Matroid/Minor/Rank.lean)

State before:
α : Type u_1
M✝ N : Matroid α
I J C D X Y Z : Set α
e f : α
M : Matroid α
h : Disjoint X D
⊢ (M ＼ D).er X = M.er X
Tactic:
rwa [delete_er_eq', sdiff_eq_left.2]
State after:
no goals