\documentclass[12pt]{article} \usepackage{amssymb,amsmath,amscd,concmath,amsfonts} \usepackage{color} \pagestyle{empty} \begin{document} \begin{equation*} y_e = -C A^{-1} B u_d =\frac{b_0 k_2}{k_0 k_2 + b_0 k_2 k}u_d. \end{equation*} \end{document}