[Tex/LaTex] Several lines of formulas to the left of one curly brace pointing to equation number

Question

How to make several lines of equations under one curly brace from the left side, such that it point to a reference number.

Now I do something like this:

\begin{align}
\left.
\begin{array}{ll}
a = b + c \\
& \dots  \\
a = b + c \\
& \dots  \\
a = b + c 
\end{array}
\right\} \label{formulas}\\
\end{align}

But equation number appears in the bottom of curly brace.

Answer 1

Looks like you have an extra line break \\ to the right of your label. If you delete it, the output should look fine.

\documentclass{article}

\usepackage{amsmath}

\begin{document}

\begin{align}
\left.
\begin{array}{ll}
a = b + c \\
& \dots  \\
a = b + c \\
& \dots  \\
a = b + c 
\end{array}
\right\} \label{formulas}
\end{align}

\end{document}