# left-align long equation in enumerate outside of item

I have a long equation in an enumerate environment that starts left-aligned with the numerical item (which is indented). I tried \noindent-ing the equation outside of the \begin{align}, but it didn't work. Example:

\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}

• What you want is not clear. Is it the indentation of the item number that you don't want? or the indentation of the equation? – Bernard Jan 24 '18 at 17:02

You can start the display with \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}


Maybe you want this, which can be obtained in two ways: with the adjustwidth environment (from changepage), or leaving the enumerate environment, inserting the maths in full text width, and resuming enumerate afterwards withe resume] option ofenumitem:

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

\begin{document}

\begin{enumerate}
\item
\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}
\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}


try:

\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{lrbox}{\restorebox}%
\hspace{\dimexpr\labelwidth-\labelsep\relax}%
\begin{minipage}{\dimexpr\textwidth-\labelwidth\relax}%
}{\end{minipage}\end{lrbox}
\usebox\restorebox
}
\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}


if you like that lef side of equation star at left text border, than change definition for restoretext change to

\newenvironment{restoretext}%
{\@parboxrestore%
`