我正在尝试将多个重叠的下划线放置在左边距。我的目标是创建一个类似于以下内容的下划线：
这是我所能得到的：
基本上，我的主要问题是将 4 放置在下支撑外面并调整下方下支撑的长度。尽管仍然找不到如何创建边距注释。我使用的代码如下。我会很感激任何帮助，谢谢！
\documentclass{article}
\setlength{\parindent}{4em}
\setlength{\parskip}{1em}
\marginparwidth=4cm
\usepackage[left=5cm, right=2cm, top=3cm]{geometry}
\usepackage{marginnote}
\usepackage{amsmath,amsfonts,amsthm}
\begin{document}
\reversemarginpar
\marginnote{$\rlap{\ensuremath{\underbrace{\phantom{1+2,\underbrace{1+2}_{3+4}}}_{5}}}\underbrace{1+2}_{3\rlap{\ensuremath{\underbrace{\phantom{1+2,\underbrace{1+2}_{3+4}}}}}}$}[1cm]
By His orders, this decision was announced to the people of Berlin on the next day.
As long as telephone connections with the bunker remained open, during the succeeding days, many followers and officials begged him to reconsider his
\end{document}
答案1
这解决了设置嵌套的主要问题\underbrace，使得括号不会互相干扰。原则上，您可以在零宽度框中设置某些内容（使用\rlap或\llap，或由提供的数学等价物mathtools) 并发出关联以获取/\phantom中缺失元素集的正确水平间距。\rlap\llap
\documentclass{article}
\begin{document}
\[
\underbrace{1 + 2}_{\textstyle \rlap{$\underbrace{3 + 4}_{\textstyle 7}$}\phantom{3}}
\]
\end{document}