Sunday, 23 November 2014

calculus - How to solve non-fractional limits like limxtoinftyx(ln5)div(1+lnx)?



I have the limit lim. I am trying to figure out how to solve this, but I only know how to handle limits when they can be made into fractions. Is there some way I can do that here, or should I try something else?



This is a homework problem, and I don't need a complete answer, but I'd appreciate some advice.


Answer



We asked to evaluate \lim \limits_{x \rightarrow \infty} x^{\frac{\ln(5)}{1+\ln(x)}} which can also be written as \lim \limits_{x \rightarrow \infty} e^{\ln(x){\frac{\ln(5)}{1+\ln(x)}}}. Using a few other rules, you can get to the following expression

e^{\ln(5) \cdot \lim \limits_{x \rightarrow \infty} \frac{\ln(x)}{1+\ln(x)} }



Now I will leave the details to you but as a hint, remind yourself of L'hospital's rule.



And finally, you can show:



\lim \limits_{x \rightarrow \infty} x^{\frac{\ln(5)}{1+\ln(x)}} = 5


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