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\begin{document}
\begin{center}
\large{\LaTeX\ Example 4}
\end{center}
Symbols of inclusion in \LaTeX\ can be scaled to match the complexity of the expression. For
example, consider
\[
(\frac{x^2+1}{x^2+x+1})(x^3+x^2-3x+1)
\]
\begin{quote}
\begin{verbatim}
\[
(\frac{x^2+1}{x^2+x+1})(x^3+x^2-3x+1)
\]
\end{verbatim}
\end{quote}
The parenthesis don't quite match the size of the fraction. This can be fixed with the \verb+\+left\verb+(+
and the \verb+\+right\verb+)+ commands:
\[
\left(\frac{x^2+1}{x^2+x+1}\right)(x^3+x2-3x+1)
\]
\begin{quote}
\begin{verbatim}
\[
\left(\frac{x^2+1}{x^2+x+1}\right)(x^3+x2-3x+1)
\]
\end{verbatim}
\end{quote}
Or, with braces:
\[
\left\{\frac{x^2+1}{x^2+x+1}\right\}(x^3+x^2-3x+1)
\]
\begin{quote}
\begin{verbatim}
\[
\left\{\frac{x^2+1}{x^2+x+1}\right\}(x^3+x^2-3x+1)
\]
\end{verbatim}
\end{quote}
Observations:
\begin{itemize}
\item Notice in the last example that the braces are each preceded by a backslash. This is
to let \LaTeX\ know that the braces are to be typeset and do not define a new scope.
\item The \verb+\+left and \verb+\+right commands must match up in pairs, although the symbols of
inclusion do not have to match. For example \verb+\+left\verb+(+ can be closed by \verb+\+right\verb+)+.
\item The symbols of inclusion \verb+[.]+ and \verb+|.|+ handled similarly.
\item \verb+\+left. and \verb+\+right. are special symbols of inclusion that are ``empty.`` They are not
typeset, but are used to maintain the \verb+\+left and \verb+\+right match that is required by
\LaTeX\.
\item Notice \verb+\+frac \verb+{+ a\verb+}{+ b\verb+}+ typsets the fractions \frac{a}{b}.
\end{itemize}
---Britney Wiggins
\end{document}
答案1
两件事情：
- 不要以
\.（第 57 行）结束你的句子。 \frac在数学模式下工作，因此使用$\frac{a}{b}$（第 58 行）。