assumption
case refine_1
α : Type u_1
A✝¹ B✝¹ I J X : Set α
M✝ : RankMatroid α
x : α
M : RankMatroid α
A✝ B✝ : Set α
hA : A✝ ⊆ B✝
hB : M.Indep B✝
P : ℕ∞ → Prop := fun n => ∀ (A B : Set α), A ⊆ B → M.Indep B → (B \ A).encard = n → M.relRank A B = n
n : ℕ∞
A B : Set α
a✝¹ : A ⊆ B
a✝ : M.Indep B
h : (B \ A).encard = 0
this : M.relRank A B = 0
⊢ M.relRank A B = 0
no goals