Writing in-line equations on multiple lines using \displaystyle

Question

I'm trying to write equations on multiple lines using \displaystyle. I can use \\ for line breaks but can't align or put horizontal space on the second line.

\documentclass[12pt,a4paper]{article}
\usepackage[latin1]{inputenc}
\usepackage{amsmath,amsfonts,amssymb}

\begin{document}

\begin{itemize}
\item $\displaystyle
(n+1)^2+5(n+1)+1 = n^2+2n+1+5n+5+1 \\
%\hspace{4em}
%%&
%\quad
= n^2+7n+7
$
\end{itemize}

\end{document}

Note that the equation is in-line and should start at the bullet point. I have made several attempts to indent the second line but the output always looks like

(Note that this is a MWE - the actual equation I'm typesetting is more complicated.) Is there a way to align the two lines of the equation at the = sign? This is indicated by the red arrow in the picture.

Answer 1

Use aligned with top vertical alignment.

\documentclass[12pt,a4paper]{article}
\usepackage{amsmath,amssymb}

\begin{document}

\begin{itemize}
\item $\begin{aligned}[t]
       (n+1)^2+5(n+1)+1 &= n^2+2n+1+5n+5+1 \\
                        &= n^2+7n+7
      \end{aligned}$
\end{itemize}

\end{document}

I removed the packages that are unnecessary for the example; amsfonts is loaded by amssymb anyway.

Are you sure you want to continue using latin1 for your documents?