如何使用 cnltx-example 编写矩阵及其源代码

Question

我想获得矩阵的输出

\begin{pmatrix}
\frac{1}{2} & 0 & \frac{9}{5} \\
-2 & \frac{2}{3} & -\frac{1}{4} \\
12 & 0 & \frac{11}{7} \\
\end{pmatrix}

以及使用并排显示的代码

\begin{example}[side-by-side]
\end{example} 

使用cnltx-example包。当我要编译（使用amsartdocumentclass）这个时，它给出错误。如何修复它？

这是我的代码

\documentclass{amsart}
\usepackage{amsmath,amsthm,amssymb,amsxtra,amsopn}
\usepackage{cnltx-example}

\begin{document}

\begin{example}[side-by-side]
  Consider the following example.
  \[ (x + y)^2 = x^2 + 2xy + y^2\]
\end{example}

%The following gives an error at the time of compiling
\begin{example}[side-by-side]
  Consider the following matrix.
$\begin{pmatrix}
\frac{1}{2} & 0 & \frac{9}{5} \\
-2 & \frac{2}{3} & -\frac{1}{4} \\
12 & 0 & \frac{11}{7} \\
\end{pmatrix}$
\end{example}

\end{document}

Answer 1

显然，cnltx-example需要将代码缩进两个空格：

\documentclass{amsart}
\usepackage{amssymb}
\usepackage{cnltx-example}

\begin{document}

\begin{example}[side-by-side]
  Consider the following example.
  \[ (x + y)^2 = x^2 + 2xy + y^2\]
\end{example}

%The following gives an error at the time of compiling
\begin{example}[side-by-side]
  Consider the following matrix.
  $\begin{pmatrix} \frac{1}{2} & 0 & \frac{9}{5} \\
  -2 & \frac{2}{3} & -\frac{1}{4} \\
  12 & 0 & \frac{11}{7} \\
  \end{pmatrix}$
\end{example}

\end{document}