Sunday, 24 July 2016

real analysis - Limit:limlimitsnrightarrowinftyleft(nbigl(1sqrt[n]ln(n)bigr)right)




I find to difficult to evaluate with lim I tried to use the fact, that \frac{1}{1-n} \geqslant \ln(n)\geqslant 1+n
what gives \lim_{n\rightarrow\infty}\left ( n\left(1-\sqrt[n]{\ln(n)} \right) \right ) \geqslant \lim_{n\rightarrow\infty} n(1-\sqrt[n]{1+n}) =\lim_{n\rightarrow\infty}n *\lim_{n\rightarrow\infty}(1-\sqrt[n]{1+n}) (1-\sqrt[n]{1+n})\rightarrow -1\Rightarrow\lim_{n\rightarrow\infty}\left ( n\left(1-\sqrt[n]{\ln(n)} \right) \right )\rightarrow-\inftyIs it correct? If not, what do I wrong?


Answer



Since it's so hard let's solve it in one line



\lim_{n\rightarrow\infty}\left ( n\left(1-\sqrt[n]{\ln(n)} \right) \right )=-\lim_{n\rightarrow\infty}\left(\frac{\sqrt[n]{\ln(n)}-1}{\displaystyle\frac{1}{n}\ln(\ln (n)) }\cdot \ln(\ln (n))\right)=-(1\cdot \infty)=-\infty.



Chris.


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