Let $x_n = \frac{1}{2} \left( x_{n-1} + \frac{5}{x_{n-1}} \right)$ for $n \geq 1$ with $x_0 = 3$. This is a well-known recursive sequence for approximating $\sqrt{5}$. If $e_n = x_n - \sqrt{5}$ represents the error at step $n$, which of the following relations correctly bounds the error $e_n$ in terms of $e_{n-1}$?