exact div_mul_eq_of_le_of_lt h₁ carry h₃
n x : ℕ
npos : 0 < n
carry : 2 ^ Nat.size x ≤ next n x
h₁ : expt n x ≤ Nat.size x
h₃ : next n x < 2 ^ Nat.size x + 2 ^ expt n x
⊢ (x + 2 ^ expt n x) / 2 ^ expt n x * 2 ^ expt n x = 2 ^ Nat.size x
no goals