I have long equation $F=\left\{ abcdef \right\}$
which needed to break line at halfway. To do it I use \begin{multline}
.
\begin{multline}
F = \left\{ abc \right.\nonumber\\
\left. {} + def \right\},
\end{multline}
I also need to break curly bracket over the multiple lines, which I do with \right.\nonumber\\
.
q1) How to align the equals sign of top line with + sign of bottom line in this case?
q2) How to display equation number?