have : d₁ ≃ a₁ := sub_eqv_diff
ℕ : Type
inst✝¹ : Natural ℕ
motive : Difference ℕ → Sort u
inst✝ : IndexedFamily motive
ctx : Induction.Context motive
n₁ m₁ n₂ m₂ : ℕ
a₁ : Difference ℕ := n₁——m₁
a₂ : Difference ℕ := n₂——m₂
x✝ : a₁ ≃ a₂
d₁ : Difference ℕ := n₁——0 - m₁——0
d₂ : Difference ℕ := n₂——0 - m₂——0
⊢ fsubst x✝ (Induction.Context.ind_diff ctx a₁) ≃ Induction.Context.ind_diff ctx a₂
ℕ : Type
inst✝¹ : Natural ℕ
motive : Difference ℕ → Sort u
inst✝ : IndexedFamily motive
ctx : Induction.Context motive
n₁ m₁ n₂ m₂ : ℕ
a₁ : Difference ℕ := n₁——m₁
a₂ : Difference ℕ := n₂——m₂
x✝ : a₁ ≃ a₂
d₁ : Difference ℕ := n₁——0 - m₁——0
d₂ : Difference ℕ := n₂——0 - m₂——0
this : d₁ ≃ a₁
⊢ fsubst x✝ (Induction.Context.ind_diff ctx a₁) ≃ Induction.Context.ind_diff ctx a₂