Definition of $\lim_{n\rightarrow+\infty}{\left({\frac{n}{n+1}}\right)^n} = e$

limits

I have the following limit

$$\lim_{n\rightarrow+\infty}{\left({\frac{n}{n+1}}\right)^n}$$

It leads to an indeterminate $[1^\infty]$, this means I should look into the limit of $e$. I rework the function a little bit:

$$\left({\frac{n}{n+1}}\right)^n=\left({\frac{n+1-1}{n+1}}\right)^n=\left({1-\frac{1}{n+1}}\right)^n$$

This is similar but not identical to

$$\left({1+\frac{1}{n}}\right)^n\rightarrow e$$

The major difference I notice is the $n+1$ in the denominator. Is the limit considered to approach $e^{-1}$ because for $n\rightarrow\infty$ we have $n+1\sim n$?

Best Answer

Remark that

$$\left(\frac n{n+1}\right)^n=\left(1+\frac1n\right)^{-n}$$ and by continuity of the reciprocal function, the limit of the reciprocal is the reciprocal of the limit.


This shows that in general $n+1\sim n$, unless there is some cancellation. (More specifically, $n+1-n\nsim n-n$.)

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