子问题中矩阵对齐存在问题

Question

请告诉我如何解决子问题中矩阵方程的对齐问题。在问题 4 (b) 中，矩阵将其位置置于中心，而我从一开始就希望它处于中心。在问题 4 的开始部分也是一样，我声明了矩阵的一般形式，它需要两行？我正在放下乳胶本身，以便有人可以在那里自行纠正它。谢谢

\documentclass[11pt,paper=a4,answers]{exam}
\usepackage{graphicx,lastpage}
\usepackage{amsmath, amsthm, amssymb, amsfonts}
\usepackage{upgreek}
\usepackage{censor}
\censorruledepth=-.2ex
\censorruleheight=.1ex
\hyphenpenalty 10000
\usepackage[paperheight=10.5in,paperwidth=8.27in,bindingoffset=0in,left=0.8in,right=1in,
top=0.7in,bottom=1in,headsep=.5\baselineskip]{geometry}
\flushbottom
\usepackage[normalem]{ulem}
\renewcommand\ULthickness{2pt}   %%---> For changing thickness of underline
\setlength\ULdepth{1.5ex}%\maxdimen ---> For changing depth of underline
\renewcommand{\baselinestretch}{1}
\pagestyle{empty}

\pagestyle{headandfoot}
\headrule
\newcommand{\continuedmessage}{%
\ifcontinuation{\footnotesize Question \ContinuedQuestion\ continues\ldots}{}%
 }
\runningheader{\footnotesize Mathematics}
{\footnotesize Mathematics --- Differential Geometry}
{\footnotesize Page \thepage\ of \numpages}
\footrule
\footer{\footnotesize Student's name:}
{}
{\ifincomplete{\footnotesize Question \IncompleteQuestion\ continues
on the next page\ldots}{\iflastpage{\footnotesize End of exam}{\footnotesize Please go        on to the next page\ldots}}}

\usepackage{cleveref}
\crefname{figure}{figure}{figures}
\crefname{question}{question}{questions}
%==============================================================


\begin{document}
\begin{questions}
\pointsinrightmargin
\pointsdroppedatright
\marksnotpoints
\pointpoints{mark}{marks}
\pointformat{\boldmath\themarginpoints}
\bracketedpoints
\question
Why is there air?

\question
What if there were no air?

\begin{parts}
\part
Describe the effect on the balloon industry.

\part
Describe the effect on the aircraft industry.
\end{parts}

\question
\begin{parts}
\part
Define the universe.  Give three examples.

\part
If the universe were to end, how would you know?
\end{parts}
\question
If $S \in Mat_{2}(\mathbb{Z})$ is of the form 
\begin{displaymath} 
\left( \begin{array}{cc} a & b \\
c & d  \\
\end{array} \right) \end{displaymath},
 then prove the following:
\begin{parts}
\part[3] $S$ is a subring of $ Mat_{2}(\mathbb{Z})$. \droppoints
\part[2] \begin{equation}\nonumber
\begin{pmatrix}
a & b  \\ c & 0
\end{pmatrix}^{k}
=
\begin{pmatrix}
a^{k} & x \\ 0 & c^{k}
\end{pmatrix}
\end{equation}
\part[3] \begin{displaymath} 
\left( \begin{array}{cc} a & b \\
c & d  \\
\end{array} \right) \end{displaymath}
\end{parts}
\end{questions}
\end{document}

Answer 1

如果您不想让方程式居中，请不要使用显示数学：

代码：

\documentclass[11pt,paper=a4,answers]{exam}
\usepackage{graphicx,lastpage}
\usepackage{amsmath, amsthm, amssymb, amsfonts}
\usepackage{upgreek}
\usepackage{censor}
\censorruledepth=-.2ex
\censorruleheight=.1ex
\hyphenpenalty 10000
\usepackage[paperheight=10.5in,paperwidth=8.27in,bindingoffset=0in,left=0.8in,right=1in,
top=0.7in,bottom=1in,headsep=.5\baselineskip]{geometry}
\flushbottom
\usepackage[normalem]{ulem}
\renewcommand\ULthickness{2pt}   %%---> For changing thickness of underline
\setlength\ULdepth{1.5ex}%\maxdimen ---> For changing depth of underline
\renewcommand{\baselinestretch}{1}
\pagestyle{empty}

\pagestyle{headandfoot}
\headrule
\newcommand{\continuedmessage}{%
\ifcontinuation{\footnotesize Question \ContinuedQuestion\ continues\ldots}{}%
 }
\runningheader{\footnotesize Mathematics}
{\footnotesize Mathematics --- Differential Geometry}
{\footnotesize Page \thepage\ of \numpages}
\footrule
\footer{\footnotesize Student's name:}
{}
{\ifincomplete{\footnotesize Question \IncompleteQuestion\ continues
on the next page\ldots}{\iflastpage{\footnotesize End of exam}{\footnotesize Please go        on to the next page\ldots}}}

\usepackage{cleveref}
\crefname{figure}{figure}{figures}
\crefname{question}{question}{questions}
%==============================================================


\begin{document}
\begin{questions}
\pointsinrightmargin
\pointsdroppedatright
\marksnotpoints
\pointpoints{mark}{marks}
\pointformat{\boldmath\themarginpoints}
\bracketedpoints
\question
Why is there air?

\question
What if there were no air?

\begin{parts}
\part
Describe the effect on the balloon industry.

\part
Describe the effect on the aircraft industry.
\end{parts}

\question
\begin{parts}
\part
Define the universe.  Give three examples.

\part
If the universe were to end, how would you know?
\end{parts}
\question
If $S \in Mat_{2}(\mathbb{Z})$ is of the form 
$ 
\left( \begin{array}{cc} a & b \\
c & d  \\
\end{array} \right) $,
 then prove the following:
\begin{parts}
\part[3] $S$ is a subring of $ Mat_{2}(\mathbb{Z})$. \droppoints
\part[2] $
\begin{pmatrix}
a & b  \\ c & 0
\end{pmatrix}^{k}
=
\begin{pmatrix}
a^{k} & x \\ 0 & c^{k}
\end{pmatrix}
$
\part[3] $ 
\left( \begin{array}{cc} a & b \\
c & d  \\
\end{array} \right) $
\end{parts}
\end{questions}
\end{document}