\documentclass[12pt]{article}
\usepackage{amssymb,amsmath,amscd,concmath,amsfonts}
\usepackage{color}
\pagestyle{empty}
\begin{document}
\begin{equation*}
      c_{f}\dot{T}_{f} = -F_{b} + F_{a}
\end{equation*}
\end{document}