![我怎样才能消除以下错误(未定义的控制序列)?](https://linux22.com/image/300298/%E6%88%91%E6%80%8E%E6%A0%B7%E6%89%8D%E8%83%BD%E6%B6%88%E9%99%A4%E4%BB%A5%E4%B8%8B%E9%94%99%E8%AF%AF%EF%BC%88%E6%9C%AA%E5%AE%9A%E4%B9%89%E7%9A%84%E6%8E%A7%E5%88%B6%E5%BA%8F%E5%88%97%EF%BC%89%EF%BC%9F.png)
请注意,此错误不会产生影响,因为我可以忽略它并继续,但我无法弄清楚是什么原因导致它发生。错误发生在最后一行; \end{flalign}
\documentclass[11pt,a4paper]{article}
\usepackage{blindtext}
\usepackage{mathtools}
\DeclareMathOperator{\sgn}{sgn}
\begin{document}
\begin{flalign*}
+ba-ba&=
+b\times (+a-a)\\
&=(+a-a)\times (+b),\\
&=-b\times (+a-a),\\
&=(+a-a)\times (-b),\\
\end{flalign*}
\begin{flalign*}
&\unalign{\text{whence}}&& 0=(+b)\times 0=0\times (+b)=(-b)\times 0=0\times (-b);\\
&\unalign{\text {or briefly}}&& b\times 0=0\times b=0.
\end{flalign*}
\end{document}
答案1
也许这就是你想要的东西?
\documentclass[11pt,a4paper]{article}
\usepackage{blindtext}
\usepackage{mathtools}
\DeclareMathOperator{\sgn}{sgn}
\begin{document}
\begin{flalign*}
+ba-ba& = +b × (+a-a)\\
& = (+a-a) × (+b),\\
& = -b × (+a-a),\\
& =(+a-a) × (-b),\\
\shortintertext{whence}
0 & =(+b) × 0=0 × (+b)=(-b) × 0=0 × (-b);\\
\shortintertext {or briefly}
& \begin{gathered} b × 0=0 × b=0. \end{gathered}
\end{flalign*}
\end{document}