simpa using length_mul_pow2_add_of_lt pos (show Pow2 2 from by simp) one_lt_two
M : Type u_1
inst✝⁵ : Zero M
inst✝⁴ : One M
inst✝³ : Add M
inst✝² : Mul M
inst✝¹ : LT M
inst✝ : M ⊧ₘ* 𝐈𝚫₀ + 𝛀₁
a : M
pos : 0 < a
⊢ ‖a * 2 + 1‖ = ‖a‖ + 1
no goals