如何改变这些公式？

Question

我想修改下图中的两个公式。你能帮我吗？

\documentclass[a4paper,12pt]{article}[12pt] 
\usepackage[italian]{babel} 
\usepackage[T1]{fontenc} 
\usepackage[utf8]{inputenc} 
\usepackage{anysize}
\usepackage{graphicx}
\usepackage{amsmath}
\usepackage{amssymb}
\usepackage{mathrsfs} 
\usepackage{textcomp} 
\linespread{1.5}

\frenchspacing 

\newcommand{\abs}[1]{\lvert#1\rvert}

\usepackage{floatflt,epsfig}

\usepackage{multicol}




  \usepackage[a4paper,top=1.0cm,bottom=1.0cm,left=1.0cm,right=1.0cm]{geometry}


\begin{document}


$ a^2 = 16 \rightarrow a = \pm 4 =  $

\newpage

$ x \cdot \left( x+3\right)  = 0 \rightarrow $




\end{document}

Answer 1

以下是如何使用pstricks 和mathtools（对于\underbracket命令）执行此操作。

无关：epsfig已经过时 20 多年了，应该用 代替graphicx。此外，从 3.10 版开始， 的语言选项babel应该与文档类一起加载，因此语言相关的包应该知道文档的语言。

\documentclass[a4paper,12pt, italian, svgnames]{article}[12pt]
\usepackage{babel}
\usepackage[T1]{fontenc}
\usepackage[utf8]{inputenc}
\usepackage{anysize}
\usepackage{graphicx}
\usepackage{amssymb}
\usepackage{mathrsfs}
\usepackage{textcomp}

\usepackage{mathtools}
\usepackage{pst-node}
\usepackage{auto-pst-pdf} %% to compile with pdflatex --enable-write18 (MiKTeX) or pdflatex --shell-escape (TeX Live, MacTeX))
\newcommand\mathpnode[1]{\pnode[0,\fontdimen22\textfont2]{#1}}

\linespread{1.5}

\frenchspacing
\DeclarePairedDelimiter{\abs}{\lvert}{\rvert}

\usepackage{floatflt}%
\usepackage{multicol}

 \usepackage[a4paper, margin=1.0cm]{geometry}

\begin{document}

\begin{pspicture}
$ a^2 = 16 \rightarrow a = \pm 4 = \mathpnode{M}\qquad\begin{aligned}
  \mathpnode{R1} & \mathbf{ + 4} \\[1ex]
  \mathpnode{R2} & \mathbf{ - 4}
\psset{nodesep = 3pt}
\ncline{M}{R1}
\ncline{M}{R2}
\end{aligned} $
\end{pspicture}
\bigskip

$\psset{fillstyle = solid} \underbracket[0.8pt]{\,x\vphantom{)}\,}_{{\substack{\vert\\\pscirclebox[fillcolor = BlanchedAlmond]{1}}}}\! \cdot \underbracket[1pt]{( x+3) }_{\substack{\vert\\\pscirclebox[fillcolor = Aqua!40]{2}}}= 0 \rightarrow \quad\begin{aligned}
 & \raisebox{-0.3\height}{\pscirclebox[fillcolor = BlanchedAlmond]{1}}\quad\mathbf{x = 0}
\\[1ex]
 & \raisebox{-0.3\height}{\pscirclebox[fillcolor = Aqua!40]{2}}\quad\mathbf{x + 3\rightarrow x = -3}
\end{aligned}$

\end{document}