在枚举项外部左对齐长方程

Question

我在枚举环境中有一个长方程，它以数字项（缩进）左对齐。我尝试\noindent将方程式放在 之外\begin{align}，但没有成功。示例：

\begin{enumerate}
\item 
\begin{align}
R(x) = really-long-equation-that-gets-forced-to-align-with-the-number-1.-but-I-want-full-left-alignment
\end{align}
\end{enumerate}

Answer 1

您可以使用以下命令启动显示\hspace{-\leftmargin}：

\documentclass{article}

\usepackage{amsmath}

\begin{document}

\noindent
Text
\begin{enumerate}
\item
  \begin{align}
  \hspace{-\leftmargin}
    R(x) = really-long-equation-that-gets-forced-to-align-with-the-number-1.-but-I-want-full-left-alignment
\end{align}
  \item Text.
\end{enumerate}
\end{document}

Answer 2

也许您想要这个，可以通过两种方式获得：使用 adjustwidth环境（来自changepage），或离开enumerate环境，以完整的文本宽度插入数学， enumerate然后使用resume] option ofenumitem 恢复：

\documentclass{article}
\usepackage[utf8]{inputenc}%
\usepackage[showframe]{geometry}
\usepackage{enumitem}
\usepackage{amsmath}
\usepackage{changepage} 

\begin{document}

\begin{enumerate}
\item 
\begin{adjustwidth}{-\leftmargini}{0cm}
\begin{align}
R(x) = \text{really-long-equation-that-gets-forced-to-align-with-the-number-1.-but-I-want-full-left-alignment}
\end{align}
\end{adjustwidth}
\item Another item.
\end{enumerate}
\vskip1cm

\begin{enumerate}[after = \leavevmode\vspace*{-\abovedisplayskip}]
\item
\end{enumerate}
\begin{align}
R(x) = \text{really-long-equation-that-gets-forced-to-align-with-the-number-1.-but-I-want-full-left-alignment}
\end{align}
\begin{enumerate}[resume]
\item Another item.
\end{enumerate}

\end{document} 

Answer 3

尝试：

\documentclass[12pt]{article}
\usepackage[showframe]{geometry}
\usepackage{amsmath}
\usepackage[strict]{changepage}
%%------------ for restoring textwidth inside list, for equations
\makeatletter
    \newsavebox\restorebox
\newenvironment{restoretext}%
    {\@parboxrestore%
        \begin{adjustwidth}{}{}%
                \begin{lrbox}{\restorebox}%
                \hspace{\dimexpr\labelwidth-\labelsep\relax}%
                \begin{minipage}{\dimexpr\textwidth-\labelwidth\relax}%
    }{\end{minipage}\end{lrbox}
        \usebox\restorebox
        \end{adjustwidth}
     }
\makeatother
\usepackage{lipsum}

\begin{document}
\begin{enumerate}
\item   \lipsum*[11]
\begin{restoretext}
\begin{gather}
R(x) = really-long-equation-that-gets-forced-to-align-with-the-number-1.-but-I-want-full-left-alignment
\end{gather}
\end{restoretext}
\item   \lipsum*[11]
\end{enumerate}
\end{document}

如果你喜欢等式左侧星号在文本左侧边框处，则将定义更改restoretext为

\newenvironment{restoretext}%
    {\@parboxrestore%
        \begin{adjustwidth}{}{}%
                \begin{lrbox}{\restorebox}%
                \begin{minipage}{\textwidth}%
    }{\end{minipage}\end{lrbox}
        \usebox\restorebox
        \end{adjustwidth}
     }

当然，这么长的方程式（比纸张宽度宽）无法适合文本宽度。如果它真的那么长，那么你应该考虑把它分成两行（或者如果有必要的话）更多行。