Can anybody please let me know what I am missing?

Question

I have type the following code.

\begin{align*}
\RR = \left\{ a_1 = \begin{pmatrix}
                     0 & 0 \\
                     0 & 0
                    \end{pmatrix},
              a_2 = \begin{pmatrix}
                     1 & 0 \\
                     0 & 0
                    \end{pmatrix},
              a_3 = \begin{pmatrix}
                     0 & 1 \\
                     0 & 0
                    \end{pmatrix},
              a_4 = \begin{pmatrix}
                     0 & 0 \\
                     0 & 1
                    \end{pmatrix}  \\
              a_5 = \begin{pmatrix}
                     1 & 1 \\
                     0 & 0
                    \end{pmatrix},
              a_6 = \begin{pmatrix}
                     0 & 1 \\
                     0 & 1
                    \end{pmatrix},
              a_7 = \begin{pmatrix}
                     1 & 1 \\
                     0 & 1
                    \end{pmatrix},
              a_8 = \begin{pmatrix}
                     1 & 0 \\
                     0 & 1
                    \end{pmatrix}       
  \right\}
\end{align*}

Answer 1

As \left ... \right doesn't work across line breaks, you can use \biggl\{ and \biggr\} instead. Judging by the image I would also suggest multline* instead of align*.

\documentclass{article}
\usepackage{amsmath}
\begin{document}
\begin{multline*}
R = \biggl\{ a_1 = \begin{pmatrix}
                     0 & 0 \\
                     0 & 0
                    \end{pmatrix},
              a_2 = \begin{pmatrix}
                     1 & 0 \\
                     0 & 0
                    \end{pmatrix},
              a_3 = \begin{pmatrix}
                     0 & 1 \\
                     0 & 0
                    \end{pmatrix},
              a_4 = \begin{pmatrix}
                     0 & 0 \\
                     0 & 1
                    \end{pmatrix},  \\
              a_5 = \begin{pmatrix}
                     1 & 1 \\
                     0 & 0
                    \end{pmatrix},
              a_6 = \begin{pmatrix}
                     0 & 1 \\
                     0 & 1
                    \end{pmatrix},
              a_7 = \begin{pmatrix}
                     1 & 1 \\
                     0 & 1
                    \end{pmatrix},
              a_8 = \begin{pmatrix}
                     1 & 0 \\
                     0 & 1
                    \end{pmatrix}       
  \biggr\}
\end{multline*}
\end{document}