如何实现单个方程式不缩进？

Question

我想要一个无缩进的单个方程完全没有。我知道我可以用它全局设置

\setlength{\mathindent}{0cm}

但我不知道算完后如何恢复到默认值。

这里是我的最小例子：

\documentclass[a4paper,12pt]{article}
\usepackage[fleqn]{amsmath}
\begin{document}

\noindent
Default indentation: 
\begin{equation}
  a+b=42
\end{equation}
%
Now I want no indention for a single equation:
\setlength{\mathindent}{0cm}
\begin{equation}
  a+b=42
\end{equation}
%
Now I'd like to get the default again:
\begin{equation}
  a+b=42
\end{equation}
%
But how?

\end{document}

Answer 1

\documentclass[a4paper,12pt]{article}
\usepackage[fleqn]{amsmath}
\begin{document}

\noindent
Default indentation: 
\begin{equation}
  a+b=42
\end{equation}
%
Now I want no indention for a single equation:
{\setlength{\mathindent}{0cm}
\begin{equation}
  a+b=42
\end{equation}}%
%
Now I'd like to get the default again:
\begin{equation}
  a+b=42
\end{equation}
%
But how?

\end{document}