答案1
我的建议:使用嵌套的equation
/aligned[b]
环境以及&\quad
(twice) 和&\qquad
(six times) 语句在第 2 行到第 9 行执行水平对齐。
\documentclass{article}
\usepackage{amsmath} % for 'aligned' environment
\usepackage{newtxtext,newtxmath} % optional
\setlength\textwidth{2in} % just for this example
\begin{document}
\setcounter{equation}{8} % just for this example
\begin{equation}
\begin{aligned}[b]
\frac{X_{12}}{i}
&= \Bigl[\Bigl\{\Bigl[(a_{k_{+}}\cdots\Bigr] \\
&\qquad+\Bigl[\Bigl(\frac{u}{v}\cdots\Bigr] \\
&\qquad+\Bigl[\Bigl(\frac{m}{n}\cdots\Bigr]\Bigr\}\Bigr] \\
&\quad -\Bigl[\Bigl\{\Bigl[\Bigl(\frac{a_{k_{+}}}{\sqrt{2}}\cdots\Bigr]\\
&\qquad+\Bigl[\Bigl(\frac{x}{z}\cdots\Bigr] \\
&\qquad+\Bigl[\Bigl(\frac{p}{q}\cdots\Bigr]\Bigr\}\Bigr] \\
&\quad +\Bigl\{\Bigl[\Bigl(a_{k_{+}}\cdots\Bigr]\\
&\qquad+\Bigl[\Bigl(\frac{f}{g}\cdots\Bigr] \\
&\qquad+\Bigl[\Bigl(\frac{k}{l}\cdots\Bigr]\Bigr\}
\end{aligned}
\end{equation}
\end{document}