I'm making a class notes slides for a math course, and some slides contains some exercises. After writing the exercise I want to make a pop up box which contain the solution for that exercise, but I have a problem in doing this.

For example, I have the following code:

```
\documentclass[9pt]{beamer}
\mode<presentation>
{
  \usetheme[width=1.4cm]{PaloAlto}      
  \usecolortheme{beaver} 
  \usefonttheme{default}
  \setbeamertemplate{navigation symbols}{}
  \setbeamertemplate{caption}[numbered]
}
\usepackage{graphicx}
\usepackage{adjustbox} 
\usepackage{pbox}
\usepackage[english]{babel}
\usepackage[utf8x]{inputenc}

\begin{document}
\begin{frame}{Chapter One}
Find the domain of the function:
$$  f(x)=\sqrt{x^{2}-4}$$

Solution.
\end{frame}
\end{document}

```

When clicking on "Solution" I want a popup box to appear and contain the solution

```
$x^{2}-4 \geq 0, x^{2}\geq 4, |x|\geq 2$

```