intros x y xs hneq
α : Type u_1
inst✝ : BEq α
⊢ ∀ (x y : α) (xs : List α), (x == y) = false → removeAll (x :: xs) [y] = x :: removeAll xs [y]
α : Type u_1
inst✝ : BEq α
x y : α
xs : List α
hneq : (x == y) = false
⊢ removeAll (x :: xs) [y] = x :: removeAll xs [y]