编译器正在向我大喊大叫，说我找不到一个美元符号。你们看到了吗？或者有其他方法可以在问题陈述中表达内联数学方程式？提前致谢。
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\documentclass[12pt]{article}
\usepackage[margin=0.75in]{geometry}
\usepackage{amsmath,amsthm,amssymb,amsfonts, enumitem, fancyhdr, color, comment, graphicx, environ}
\pagestyle{fancy}
\setlength{\headheight}{65pt}
\newenvironment{problem}[2][Problem]{\begin{trivlist}
\item[\hskip \labelsep {\bfseries #1}\hskip \labelsep {\bfseries #2.}]}{\end{trivlist}}
\newenvironment{sol}
{\emph{Solution:}
}
{
\qed
}
\specialcomment{com}{ \color{blue} \textbf{Comment:} }{\color{black}} %for instructor comments while grading
\NewEnviron{probscore}{\marginpar{ \color{blue} \tiny Problem Score: \BODY \color{black} }}
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%Fill in the appropriate information below
\lhead{Student}
\rhead{Professor \\ MAT 2250 \\ 9.18.19 \\ HW 1 Solutions}
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%Do not alter this block.
\begin{document}
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%Copy the following block of text for each problem in the assignment.
\begin{problem}{1.2.11}
Find the general solution of the system whose augmented matrix is given below.
$$
\quad
\begin{bmatrix}
3 & -4 & 2 & 0 \\
-9 & 12 & -6 & 0 \\
-6 & 8 & -4 & 0 \\
\end{bmatrix}
\quad
$$
\end{problem}
\begin{sol}
\end{sol}
\begin{problem}{1.3.25}
Let $$A = \begin{bmatrix}
1 & 0 & -4 \\
0 & 3 & -2 \\
-2 & 6 & 3 \\
\end{bmatrix}$$ and \textbf{b}=
$$\begin{bmatrix}
4 \\
1 \\
-4\\
\end{bmatrix}.$$
Denote the columns of $A$ by \textbf{a_1},\textbf{a_2},\textbf{a_3}, and let $W$ = \textrm{Span}\{\textbf{a_1},\textbf{a_2},\textbf{a_3}\}.
\end{problem}
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%Do not alter anything below this line.
\end{document}
答案1
我很好奇它是什么样子的，所以我听从了@peter-grill的建议，更新后的代码运行良好：
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
\documentclass[12pt]{article}
\usepackage[margin=0.75in]{geometry}
\usepackage{amsmath,amsthm,amssymb,amsfonts, enumitem, fancyhdr, color, comment, graphicx, environ}
\pagestyle{fancy}
\setlength{\headheight}{65pt}
\newenvironment{problem}[2][Problem]{\begin{trivlist}
\item[\hskip \labelsep {\bfseries #1}\hskip \labelsep {\bfseries #2.}]}{\end{trivlist}}
\newenvironment{sol}
{\emph{Solution:}
}
{
\qed
}
\specialcomment{com}{ \color{blue} \textbf{Comment:} }{\color{black}} %for instructor comments while grading
\NewEnviron{probscore}{\marginpar{ \color{blue} \tiny Problem Score: \BODY \color{black} }}
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%Fill in the appropriate information below
\lhead{Student}
\rhead{Professor \\ MAT 2250 \\ 9.18.19 \\ HW 1 Solutions}
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%Do not alter this block.
\begin{document}
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%Copy the following block of text for each problem in the assignment.
\begin{problem}{1.2.11}
Find the general solution of the system whose augmented matrix is given below.
\[
\quad
\begin{bmatrix}
3 & -4 & 2 & 0 \\
-9 & 12 & -6 & 0 \\
-6 & 8 & -4 & 0 \\
\end{bmatrix}
\quad
\]
\end{problem}
\begin{sol}
\end{sol}
\begin{problem}{1.3.25}
Let \[A = \begin{bmatrix}
1 & 0 & -4 \\
0 & 3 & -2 \\
-2 & 6 & 3 \\
\end{bmatrix}\] and \textbf{b}=
\[\begin{bmatrix}
4 \\
1 \\
-4\\
\end{bmatrix}.\]
Denote the columns of $A$ by \textbf{$a_1$},\textbf{$a_2$},\textbf{$a_3$}, and let $W$ = \textrm{Span}\{\textbf{$a_1$},\textbf{$a_2$},\textbf{$a_3$}\}.
\end{problem}
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%Do not alter anything below this line.
\end{document}