Saturday, January 16, 2016

analysis - How to show that $lim_{n to +infty} n^{frac{1}{n}} = 1$?



I've spent the better part of this day trying to show from first principles that this sequence tends to 1. Could anyone give me an idea of how I can approach this problem?


$$ \lim_{n \to +\infty} n^{\frac{1}{n}} $$


Answer



You can use $\text{AM} \ge \text{GM}$.


$$\frac{1 + 1 + \dots + 1 + \sqrt{n} + \sqrt{n}}{n} \ge n^{1/n} \ge 1$$


$$ 1 - \frac{2}{n} + \frac{2}{\sqrt{n}} \ge n^{1/n} \ge 1$$


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