%% formulation
\documentclass{standalone}
\usepackage{amsmath}
\usepackage{bm}
\usepackage{graphicx}
\usepackage{xcolor}
\begin{document}
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\begin{align*}
\min_{u(t)} \quad & x_2(1) \\
\text{subject to:} \quad & \dot{\bm{x}}(t) = \begin{bmatrix} \frac{u(t)}{2 x_1(t)} \\ 4 [x_1(t)]^4 + [u(t)]^2 \end{bmatrix} \\
& \bm{x}(0) = (1,0) \\
&\sqrt{0.4} \leq  x_1(t) \\
& -1 \leq u(t)
\end{align*}
}}
\end{document}

%% solution