Challenge 15: There exists k ∈ ℕ such that, for all n ∈ ℕ, (n + k)² ≤ 2ⁿ⁺ᵏ
Prove that there exists \(k ∈ ℕ\) such that, for all \(n \in ℕ\), \((n + k)^{2} ≤ 2^{n+k}\).
To do so, complete the following Lean 4 theory:
import Mathlib.Tactic example : ∃ k : ℕ, ∀ n : ℕ, (n + k) ^ 2 ≤ 2 ^ (n + k) := by sorry