Sunday, May 8, 2016

limits - Prove that limntoinftyleft(1+frac1n2right)n3=+infty



I'm trying to prove that lim using the fact that if b_n\ge a_n eventually, and \lim_{n\to \infty}{a_n}=+\infty, then \lim_{n\to \infty}{b_n}=+\infty, where b_n:=n^n.




I'm struggling to show that b_n\ge a_n by induction. Is this a good method? If so, what would be the best way to proceed. Thank you in advance.


Answer



Using my comment: for almost all \;n\in\Bbb N\; , we have that (since \;e=2.7...\;)



2.5\le\left(1+\frac1{n^2}\right)^{n^2}\le3\implies\left[\left(1+\frac1{n^2}\right)^{n^2}\right]^n\ge(2.5)^n\xrightarrow[n\to\infty]{}\infty


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