将文本放置在案例环境中

Question

我怎样才能将文本放在(a case)最后一个括号的末尾？

\begin{align}
    P_{12}=
    \begin{cases} 
    \begin{split}
   -\biggl(\left [ \text{Some expression here} \right ]\\-\left [ \text{Some expression here}\right ]\biggr)
    \end{split} 
    \text{a case}
    \end{cases}   
\end{align}

Answer 1

以下情况之一 [双关语]？我不清楚您是否要将“一个案例”和“另一个案例”垂直居中放置或放置在表达式的左下方。

\documentclass{article} % or some other suitable document class

\usepackage{mathtools}  % for 'dcases' env.

\begin{document}

\begin{equation}
P_{12}= 
\begin{dcases}
\begin{aligned}
-\Bigl( [ \text{Some expression here}]& \\
-       [ \text{Some expression here}]& \Bigr)
\end{aligned} 
& \text{a case}  \\[3ex]
\begin{aligned}[b]
-\Bigl( [ \text{Some expression here}]& \\
-       [ \text{Some expression here}]& \Bigr)
\end{aligned} 
& \text{another case} 
\end{dcases}
\end{equation}

\end{document}