\documentclass{article}
\usepackage{amsmath}
\usepackage{amssymb}
\usepackage{amsfonts}

\thispagestyle{empty}
\begin{document}
\[
\dfrac{a}{b} = \dfrac{a + b}{a} = 1 + \dfrac{b}{a}
\]
\end{document}
