\documentclass[12pt]{article}
\usepackage{amssymb,amsmath,amscd,amstext,amsopn,amscd,amsfonts}
\pagestyle{empty}
\begin{document}
\begin{displaymath}synthesisRate = \frac{nbGeneCopies*maxSynthesisRate*[activator]^{n}}{K^{n}+[activator]^{n}} \end{displaymath}
\end{document}
