\documentclass[12pt]{article}
\usepackage[latin1]{inputenc}
\usepackage{amsmath}
\usepackage{amsfonts}
\RequirePackage{amsmath,amssymb,latexsym}
\pagestyle{empty}
\begin{document}
$  \alpha=x_{b}-x_{a},\beta=y_{b}-y_{a}  $
\end{document}
