我怎样才能将长公式 (2.1) 放入边距内？由于公式是分数，因此使用两行无法达到我的目的。请参阅下面的代码：
编辑：@Bernard 建议使用 \splitfrac 与 mathtool 包一起使用，但是当我们将 breqn 包与其一起使用时，在分割分数中会引入标签“1”。
% ----------------------------------------------------------------
%
% (CMDE) Computational Methods for Differential Equations, University of Tabriz, Tabriz, Iran.
%
%LaTeX Paper ************************************************
% **** --------------------------------------------------------------------------------
\documentclass[fleqn,reqno,11pt]{amsart}
%---------------------------------------------------------------------------------------
\usepackage[pdftex,marginratio=1:1,width=130mm,height=190mm,top=40mm,headsep=17mm,head=7mm,footskip=11.29mm]{geometry}
\usepackage[colorlinks,linkcolor=blue,citecolor=magenta,anchorcolor=blue,bookmarksopen,pdfpagetransition={Wipe}]{hyperref}
\usepackage{graphicx}
%---------------------------------------------------------------------------------------
% THEOREMS -----------------------------------------------------------------------
\newtheorem{thm}{Theorem}[section]
\newtheorem{cor}[thm]{Corollary}
\newtheorem{lem}[thm]{Lemma}
\newtheorem{pro}[thm]{Proposition}
\theoremstyle{definition}
\newtheorem{defn}[thm]{Definition}
\newtheorem{rem}[thm]{Remark}
\numberwithin{equation}{section}
% MATH ------------------------------------------------------------------------------
\newcommand{\norm}[1]{\left\Vert#1\right\Vert}
\newcommand{\abs}[1]{\left\vert#1\right\vert}
\newcommand{\set}[1]{\left\{#1\right\}}
% --------------------------------------------------------------------------------------
\begin{document}
\unitlength 1cm\begin{picture}(0,0)\put(2,1){ \scriptsize
\textbf{(CMDE)} \textsl{Computational Methods for Differential
Equations}}\end{picture}
\title[Please insert short title(at most 10 word)]{Please insert title}%
\author[F. Author]{First Author}%
\address{address 1}%
\email{email 1}%
\author[S. Author]{Second Author$^*$}%
\address{address 2}%
\email{email 2}%
\thanks{$*$ corresponding}
\author[T. Author]{Third Author}%
\address{address 2}%
\email{email 2}%
\subjclass[2010]{65L05, 34K06, 34K28.}
\keywords{Keyword1, keyword2, keyword3.}
%\date{}%
%\dedicatory{}%
%\commby{}%
% ----------------------------------------------------------------
\begin{abstract}
Abstract is required and should summarize, in less
than 300 words, the context, content and conclusions of the
paper. It should not contain any references or displayed
equations.
\end{abstract}
\maketitle
% ----------------------------------------------------------------
\section{Introduction}
Contributions must be in English. Authors are encouraged to have
their contribution checked for grammar. Abbreviations are allowed but
should be spelt out in full when first used. Integers ten and below
are to be spelt out but type as (2+1) dimensions. Italicize foreign
language phrases (e.g.~Latin, French).
\section{Equations}
Displayed equations should be numbered consecutively in each
section, with the number set flush right and enclosed in
parentheses.
\begin{align}
\label{56}A_{12}=\frac{\alpha_{1}^{3}\beta_{2}+3\alpha_{1}^{2}\alpha_{2}\beta_{1}-3\alpha_{1}^{2}\alpha_{2}\beta_{2}-3\alpha_{1}\alpha_{2}^{2}\beta_{1}+3\alpha_{1}\alpha_{2}^{2}\beta_{2}+\alpha_{2}^{3}\beta_{1}-6\alpha_{1}\alpha_{2}+2\beta_{1}\gamma_{2}+2\beta_{2}\gamma_{1}}{\alpha_{1}^{3}\beta_{2}+3\alpha_{1}^{2}\alpha_{2}\beta_{1}+3\alpha_{1}^{2}\alpha_{2}\beta_{2}+3\alpha_{1}\alpha_{2}^{2}\beta_{1}+3\alpha_{1}\alpha_{2}^{2}\beta_{2}+\alpha_{2}^{3}\beta_{1}-6\alpha_{1}\alpha_{2}+2\beta_{1}\gamma_{2}+2\beta_{2}\gamma_{1}}
\end{align}
\end{document}
% ----------------------------------------------------------------
答案1
您可以使用\splitfrac 命令，从mathtools
\documentclass[fleqn,reqno,11pt]{amsart}
\usepackage[pdftex,marginratio=1:1,width=130mm,height=190mm,top=40mm,headsep=17mm,head=7mm,footskip=11.29mm]{geometry}
\usepackage[colorlinks,linkcolor=blue,citecolor=magenta,anchorcolor=blue,bookmarksopen,pdfpagetransition={Wipe}]{hyperref}
\usepackage{graphicx}
\newtheorem{thm}{Theorem}[section]
\newtheorem{cor}[thm]{Corollary}
\newtheorem{lem}[thm]{Lemma}
\newtheorem{pro}[thm]{Proposition}
\theoremstyle{definition}
\newtheorem{defn}[thm]{Definition}
\newtheorem{rem}[thm]{Remark}
\numberwithin{equation}{section}
\newcommand{\norm}[1]{\left\Vert#1\right\Vert}
\newcommand{\abs}[1]{\left\vert#1\right\vert}
\newcommand{\set}[1]{\left\{#1\right\}}
\usepackage{mathtools}
\begin{document}
\unitlength 1cm\begin{picture}(0,0)\put(2,1){ \scriptsize
\textbf{(CMDE)} \textsl{Computational Methods for Differential
Equations}}\end{picture}
\title[Please insert short title(at most 10 word)]{Please insert title}%
\author[F. Author]{First Author}%
\address{address 1}%
\email{email 1}%
\author[S. Author]{Second Author$^*$}%
\address{address 2}%
\email{email 2}%
\thanks{$*$ corresponding}
\author[T. Author]{Third Author}%
\address{address 2}%
\email{email 2}%
\subjclass[2010]{65L05, 34K06, 34K28.}
\keywords{Keyword1, keyword2, keyword3.}
%\date{}%
%\dedicatory{}%
%\commby{}%
% ----------------------------------------------------------------
\begin{abstract}
Abstract is required and should summarize, in less
than 300 words, the context, content and conclusions of the
paper. It should not contain any references or displayed
equations.
\end{abstract}
\maketitle
% ----------------------------------------------------------------
\section{Introduction}
Contributions must be in English. Authors are encouraged to have
their contribution checked for grammar. Abbreviations are allowed but
should be spelt out in full when first used. Integers ten and below
are to be spelt out but type as (2+1) dimensions. Italicize foreign
language phrases (e.g.~Latin, French).
\section{Equations}
Displayed equations should be numbered consecutively in each
section, with the number set flush right and enclosed in
parentheses.
\begin{align}
\label{56}A_{12}=\frac{\splitfrac{\alpha_{1}^{3}\beta_{2}+3\alpha_{1}^{2}\alpha_{2}\beta_{1}-3\alpha_{1}^{2}\alpha_{2}\beta_{2}
-3\alpha_{1}\alpha_{2}^{2}\beta_{1}+3\alpha_{1}\alpha_{2}^{2}\beta_{2}}{+\alpha_{2}^{3}\beta_{1}-6\alpha_{1}\alpha_{2}+2\beta_{1}\gamma_{2}
+2\beta_{2}\gamma_{1}}}%
{\splitfrac{\alpha_{1}^{3}\beta_{2}+3\alpha_{1}^{2}\alpha_{2}\beta_{1}+3\alpha_{1}^{2}\alpha_{2}\beta_{2}+3\alpha_{1}\alpha_{2}^{2}\beta_{1}
+3\alpha_{1}\alpha_{2}^{2}\beta_{2}}{+\alpha_{2}^{3}\beta_{1}-6\alpha_{1}\alpha_{2}+2\beta_{1}\gamma_{2}+2\beta_{2}\gamma_{1}}}
\end{align}
\end{document}
