Monday, March 5, 2018

calculus - Help with a limit using $ln$ and l'Hôpital



I need help with the following limit:
$$\lim\limits_{n\to\infty} \left(\frac{\left(1+\frac{1}{n}\right)^{n}}{e}\right)^{n}$$




I tried using $\ln$, taking out the $n$, writing it as $\frac{1}{n}$ in the denominator and performing l'Hôpital (and then using the exponent to get the limit). But for some reason I'm not reaching the correct limit. I would greatly appreciate if someone could show me steps for solving this limit. Thank you.


Answer



Hint:



$$
\begin{align}
\lim_{n \to \infty} n\big(n \ln(1+\frac{1}{n})-1\big) & = \lim_{x \to 0^+} \frac{1}{x}\big(\frac{1}{x} \ln(1+x)-1\big) = \\
&= \lim_{x \to 0^+} \frac{\ln(1+x)-x}{x^2} \\
&= \lim_{x \to 0^+} \frac{\cfrac{1}{1+x}-1}{2 x} = \cdots \\
\end{align}

$$


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