Đặt \(t=x-e\Rightarrow\begin{cases}x=t+e\\x\rightarrow e;t\rightarrow0\end{cases}\)
\(\Rightarrow L=\lim\limits_{t\rightarrow0}\frac{\ln\left(t+e\right)-\ln e}{t}=\lim\limits_{t\rightarrow0}\frac{\ln\left(\frac{t+e}{e}\right)}{t}=\lim\limits_{t\rightarrow0}\left[\frac{\ln\left(1+\frac{t}{e}\right)}{\frac{t}{e}}\right]=\frac{1}{e}\)