%% formulation
\documentclass{standalone}
\usepackage{amsmath}
\usepackage{bm}
\usepackage{graphicx}
\usepackage{xcolor}
\begin{document}
\setlength{\abovedisplayskip}{2pt}
\setlength{\belowdisplayskip}{2pt}
\pagecolor{white}
\scalebox{2}{\parbox{0.1\textwidth}{%
\begin{align*}
\min_{\bm{u}(t)} \quad & \int_{t_0}^{t_f} \bm{u}^T \bm{I} \bm{u}\ \mathrm{d}t \\
\text{subject to:} \quad & \dot{\bm{x}} = \bm{A} \bm{x} + \bm{B} \bm{u} \\
& \bm{x}(t_0) = \bm{x}_0 \\
& \bm{x}(t_f) = \bm{x}_f
\end{align*}
}}
\end{document}

%% solution