\documentclass[12pt]{article}
\usepackage{amssymb,amsmath,amscd,concmath,amsfonts}
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\begin{document}
\begin{equation*}
    \frac{d}{dt}\begin{bmatrix} p \\ \theta \\ \dot p \\ \dot \theta \end{bmatrix} =
    \begin{bmatrix} \dot p \\ \dot \theta \\
      \dfrac{
        - m l s_\theta \dot\theta^2 
        + m g (m l^2 / J_t) s_\theta c_\theta 
	- c \dot p - (\gamma/J_t) m l c_\theta \dot\theta
        + u}
        {M_t - m (m l^2 / J_t) c_\theta^2  } \\[2ex]
      \dfrac{
	- m l^2 s_\theta c_\theta \dot\theta^2 
        + M_t g l s_\theta 
        - c l c_\theta \dot p - \gamma (M_t/m) \dot \theta
	+ l c_\theta u}
        {J_t (M_t/m) - m (l c_\theta)^2}
    \end{bmatrix}.
\end{equation*}
\end{document}