Fuente TeX:

\displaystyle \left| \frac{n}{\sqrt{n^2+1}} - 1\right| = \frac{1}{\sqrt{n^2+1}(\sqrt{n^2+1}+n)} < \frac{1}{\sqrt{n^2+1}\sqrt{n^2+1}} = \frac{1}{n^2+1}