在 $\left(\frac{dB}{dA}\right)^2\right$ 上添加下支撑

Question

我正在尝试添加 underbrace $\left(\frac{dB}{dA}\right)^2\right$。我已经添加了\underbrace{\left(\frac{dB}{dA}\right)^2\right}_\text{(-)}。

但是，LaTeX 给出了错误。我必须为此安装一个包吗？

编辑：我有以下包裹：

\usepackage{graphicx}

\usepackage{amssymb,amsthm}

\usepackage{natbib}

\bibpunct{(}{)}{;}{;}{,}{,}

\usepackage{xr-hyper}

\usepackage[
  colorlinks=true,
  citecolor=blue,
  urlcolor=blue,
  linkcolor=blue
]{hyperref}

\usepackage{bm}

\usepackage{fullpage}

\usepackage{ amssymb }

    \pagestyle{plain}

\setlength{\parskip}{\baselineskip}
\setlength{\parindent}{0pt}

\setcounter{secnumdepth}{2}

\allowdisplaybreaks[4]

% Commenting/debugging
\let\IG\iffalse
\let\ENDIG\fi

%% Shortcuts
\newcommand{\td}[2]{\dfrac{d #1}{d #2}}
\newcommand{\std}[2]{\dfrac{d^2 #1}{d {#2}^2}}
\newcommand{\ctd}[3]{\dfrac{d^2 #1}{d #2 d #3}}

\newcommand{\pd}[2]{\dfrac{\partial #1}{\partial #2}}
\newcommand{\spd}[2]{\dfrac{\partial^2 #1}{\partial {#2}^2}}
\newcommand{\cpd}[3]{\dfrac{\partial^2 #1}{\partial #2 \partial #3}}

\newcommand{\pdi}[2]{\partial #1/\partial #2}

\newcommand{\LR}{\Leftrightarrow}
\newcommand{\Lg}{\mathcal{L}}
\newcommand{\half}{\tfrac{1}{2}}
\newcommand{\eqp}{\phantom{=}}
\newcommand{\eqs}{\buildrel s \over =}

\begin{document}
\end{document}

\thispagestyle{empty}
    \frac{d^2B}{dA^2}=-\frac{1}{\underbrace{(1-p)U'(B)}_\text{(+)}}\left[\underbrace{p U''(A)}_\text{(-)} + \underbrace{(1-p)U''(B)}_\text{(-)}\left(\frac{dB}{dA}\right)^2\right]>0.

我想添加大括号\left(\frac{dB}{dA}\right)。

Answer 1

\underbrace如何使用支柱对 s 进行垂直对齐：

\documentclass{article}

\usepackage{amsmath}

\begin{document}
\[
  \newcommand{\tempstrut}{\rule[-1.2\baselineskip]{0pt}{1.5\baselineskip}}
  \frac{\mathrm{d}^2B}{\mathrm{d}A^2} =
    - \underbrace{\tempstrut\frac{1}{(1-p)U'(B)}}_{(+)}
    \Bigg[\underbrace{\tempstrut p U''(A)}_{(-)} 
      + \underbrace{\tempstrut (1-p)U''(B)}_{(-)}
      \underbrace{\tempstrut\Bigg(\frac{\mathrm{d}B}{\mathrm{d}A}\Bigg)^2}_{(+)}\Bigg] > 0.
\]
\end{document}

Answer 2

\documentclass{article}
\usepackage{graphicx}

\usepackage{amsmath,amssymb}


\begin{document}
\[
\frac{d^2B}{dA^2}=-\frac{1}{\underbrace{(1-p)U'(B)}_{\text{(+)}}}\Biggl[\underbrace{p U''(A)}_{\text{(-)}} + \underbrace{(1-p)U''(B)}_{\text{(-)}}
\underbrace{\left(\frac{dB}{dA}\right)^2}_{\text{(+)}}\Biggr]>0.
\]
\end{document}