\documentclass[12pt]{article}
\usepackage{amssymb,amsmath,amscd,concmath,amsfonts}
\usepackage{color}
\pagestyle{empty}
\begin{document}
\begin{equation*}
    A = \begin{bmatrix} 0.5 & 1 \\ 0 & 0.25 \end{bmatrix}
\end{equation*}
\end{document}