bmatrix test - nschloe/purple-pi GitHub Wiki
No spaces:
A = \begin{bmatrix}
a & b \\
c & d
\end{bmatrix}
One space:
A = \begin{bmatrix}
a & b \\
c & d
\end{bmatrix}
Two spaces:
A = \begin{bmatrix}
a & b \\
c & d
\end{bmatrix}