`pmatrix` line break

Question

I wrote a matrix using the pmatrix environment. The content is very long and LaTeX produces an output of the kind (the "a" line extending beyond \textwidth):

( aaa aaa aaa aaa aaa aaa + aaa aaa aaa )
( bb bb bb bb bb bb bb bb               )
( cccccccccccccccccc                    )

I would like to get:

( aaa aaa aaa aaa aaa aaa )
(           + aaa aaa aaa ) [aligned right]
( bb bb bb bb bb bb bb bb )
( cccccccccccccccccc      ) 

Can someone please help me? Here is a minimal example:

\documentclass{article}
\usepackage{amsmath}
\begin{document}
$\begin{pmatrix}
    aaa aaa aaa aaa aaa aaa + aaa aaa aaa \\
    bb bb bb bb bb bb bb bb\\
    cccccccccccccccccc
\end{pmatrix}$
\end{document}

Answer 1

The only problem with simply adding an extra line break is the alignment, which you can fix by adding a \hfill.

\documentclass{article}
\usepackage{amsmath}
\begin{document}
$\begin{pmatrix}
    aaa aaa aaa aaa aaa aaa \\
   \hfill + aaa aaa aaa \\
    bb bb bb bb bb bb bb bb\\
    cccccccccccccccccc
\end{pmatrix}$
\end{document}