我的 MWE：
\documentclass[]{report}
\usepackage{amsmath}
\begin{document}
\begin{align}
\dot{V} &=\, \frac{1}{\gamma_{2,1}}\sigma_{2,1} \dot{\sigma}_{2,1} + \frac{1}{\gamma_{2,2}}\sigma_{2,2} \dot{\sigma}_{2,2} + \frac{1}{\gamma_{2,3}}\sigma_{2,3} \dot{\sigma}_{2,3} \notag \\
&= -\sigma_{2,1}\left [ \sigma_{2,1}\sin^2(x_1)+\sigma_{2,2}\sin(x_1)x_2 + \sigma_{2,3}\sin(x_1)u\right ] \notag \\
& -\sigma_{2,2}\left [ \sigma_{2,1}\sin(x_1)x_2+\sigma_{2,2}x_2^2 + \sigma_{2,3}x_2 u\right ] - \sigma_{2,3}\left [ \sigma_{2,1}\sin(x_1)u+\sigma_{2,2}x_2u + \sigma_{2,3} u^2\right ]\notag \\
\end{align}
\end{document}
结果：
我想要的是：
答案1
使用
&\mathrel{\phantom{=}} - ....
在最后一行放入一个等于等号的空格