Friday, 25 November 2016

real analysis - Find the limit of this sequence $lim_{nto infty}frac{n}{1 + frac{1}{n}} - n$



Find the limit of this sequence $$\lim_{n\to \infty}\frac{n}{1 + \frac{1}{n}} - n$$



First I tried dividing everything by $n$ but that would leave me with $$\lim_{n\to \infty}\frac{1}{\frac{1}{n} + \frac{1}{n^2}} - 1$$



and as $n\to \infty$ i'd be left with $\frac{1}{0} - 1$. Would I be correct in saying that the limit is -1 or does the $\frac{1}{0}$ mess that up?


Answer



The limit is $-1$ but the $\frac{1}{0} $ does mess it up.




Just add the fractions:



you get $$\frac{n^2}{n+1} - n = \frac{n^2 - n^2 - n}{n} = \frac{-n}{n+1}$$



Finding the limit should now be easy


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