Make matrices in TEX code example

Example 1: matrix latex

\begin{bmatrix}
1 & 2 & 3 \\
a & b & c \\
a & b & c \\
\end{bmatrix}

Example 2: how to make matrix latex

\documentclass{article}
\usepackage[utf8]{inputenc}
\usepackage{amsmath}
\begin{document}
$$
\begin{bmatrix} 
a & b & c \\
c & d & d\\
e & f & g \\
\end{bmatrix}
\quad
$$
\end{document}