当使用下面的文档时，我总是收到一些奇怪的错误，例如
“糟糕的数学环境分隔符。$$[”
使用数学环境时。完整列表如下。你能告诉我该怎么做才能解决这个问题吗？
\usepackage[a4paper,left=3cm,right=3cm,top=3cm,bottom=3cm]{geometry}
\usepackage{amsfonts}
\usepackage{amsmath}
\usepackage{amssymb}
\usepackage{amsthm}
\usepackage{enumitem}
\usepackage{fancyhdr}
\usepackage[T1]{fontenc}
\usepackage{graphicx}
\usepackage[utf8]{inputenc}
\usepackage{latexsym}
\usepackage{lmodern}
\usepackage{mathtools}
\usepackage{mdframed}
\usepackage{pgf}
\usepackage{tcolorbox}
\usepackage{tikz}
\usepackage[absolute,overlay]{textpos}
\usepackage{xcolor}
\makeatletter
\renewcommand*\env@matrix[1][*\c@MaxMatrixCols c]{%
\hskip -\arraycolsep
\let\@ifnextchar\new@ifnextchar
\array{#1}}
\makeatother
\DeclareGraphicsExtensions{.pdf,.png,.jpg, .tif}
\pagestyle{fancy}
\fancyhf{}
\renewcommand{\headrulewidth}{0pt}
\fancyfoot[LE,RO]{\thepage}
\renewcommand{\familydefault}{\sfdefault}
\newcommand{\norm}[1]{\left\lVert#1\right\rVert}
\DeclarePairedDelimiter{\closed}{[}{]}
\DeclarePairedDelimiter{\oc}{\left]}{\right[}
\DeclarePairedDelimiter{\abs}{\lvert}{\rvert}
\DeclarePairedDelimiter{\biggabs}{\bigg\lvert}{\bigg\rvert}
\DeclarePairedDelimiter\ceil{\lceil}{\rceil}
\DeclarePairedDelimiter\floor{\lfloor}{\rfloor}
\tcbuselibrary{theorems}
\newtcbtheorem[number within=section]{definition}{Definition}
{colback=blue!25,colframe=blue!25!black,fonttitle=\bfseries}{th}
\newtcbtheorem[number within=section]{lemma}{Lemma}
{colback=blue!25,colframe=blue!25!black,fonttitle=\bfseries}{th}
\newtcbtheorem[number within=section]{theorem}{Theorem}
{colback=blue!25,colframe=blue!25!black,fonttitle=\bfseries}{th}
\newtcbtheorem[number within=section]{corollary}{Corollary}
{colback=blue!25,colframe=blue!25!black,fonttitle=\bfseries}{th}
\renewcommand*{\proofname}{Beweis}
\newtheorem{assumption}{Assumption}
\newtheorem*{example*}{Example}
\newtheorem{reminder}{Reminder}
\begin{document}
\title{\textbf{Sheet 6}}
\date{}
\maketitle
\begin{enumerate}
\setcounter{enumi}{26}
\item
\item
\begin{enumerate}[label=\alph*)]
\item
\item
\end{enumerate}
\item
\begin{enumerate}[label=\alph*)]
\item
$$\[
\begin{bmatrix}[ccccc|c]
x_{11} & x_{12} & x_{13} & \cdots & x_{1n} & a_{1,n+1} \\
x_{21} & x_{22} & x_{23} & \cdots & x_{2n} & a_{2,n+1} \\
\vdots & \vdots & \vdots & \ddots & \vdots & \vdots \\
x_{d1} & x_{d2} & x_{d3} & \cdots & x_{dn} & a_{d,n+1}
\end{bmatrix}
\]$$
\end{enumerate}
\item
\begin{enumerate}[label=\alph*)]
\item
\item
\end{enumerate}
\end{enumerate}
\end{document}
Bad math environment delimiter. $$\[
Missing \endgroup inserted. \]
\begin{enumerate} on input line 98 ended by \end{equation*}. \]
Missing $ inserted.
Missing } inserted.
Display math should end with $$.
Extra }, or forgotten \endgroup.
Lonely \item--perhaps a missing list environment. \begin
Undefined control sequence. \end{enumerate}
Undefined control sequence. \end{enumerate}
Missing number, treated as zero. \end{enumerate}
Undefined control sequence. \end{enumerate}
Undefined control sequence. \end{enumerate}
Missing number, treated as zero. \end{enumerate}
Undefined control sequence. \end{enumerate}
Undefined control sequence. \end{enumerate}
Undefined control sequence. \end{enumerate}
You can't use `\relax' after \the. \end{enumerate}
Undefined control sequence. \end{enumerate}
Missing number, treated as zero. \end{enumerate}
Undefined control sequence. \end{enumerate}
Undefined control sequence. \end{enumerate}
Missing number, treated as zero. \end{enumerate}
Undefined control sequence. \end{enumerate}
Undefined control sequence. \end{enumerate}
You can't use `\relax' after \the. \end{enumerate}
\begin{document} ended by \end{enumerate}. \end{enumerate}
Extra \endgroup. \end{enumerate}
inputenc package ignored with utf8 based engines.
\fancyfoot's `E' option without twoside option is useless
No \author given.
Underfull \hbox (badness 10000) detected