How can I print multiple pages on a single page via my iPhone?

The solution below uses \mathclap from the mathtools package.

This command tells TeX that the content of \mathclap should not take up any horizontal space (from TeX's point of view), which means that TeX will not extend the fraction bar to account for the content of the overbrace and underbrace

\documentclass{article}

\usepackage{amsmath}
\usepackage{mathtools}

\begin{document}

\[
\frac{x^n}{x^m}\cdot \frac{1+{\overbrace{\textstyle \frac{1}{x^n}}^{\mathclap{\geq -\frac{1}{2} \text{ for }|x| \text{ large enough}}}}}
                         {1+{\underbrace{\textstyle \frac{1}{x^m}}_{\mathclap{\leq 1 \text{ for }|x| \text{ large enough}}}}}
\]

\end{document}

And if you change the \mathclap to \mathrlap, then you get