Using TeX Notation 4
From MoodleDocs
Matrices
A Matrix is a rectangular array of numbers arranged in rows and columns which can be used to organize numeric information. Matrices can be used to predict trends and outcomes in real situations - i.e. polling.
A matrix can be written and displayed like 
In this case the matrix is constructed using the brackets before creating the array:
$$ M = \left[\begin{array} a&b&1 \ c&d&2 \ e&f&3\end{array}\right] $$
The internal structure of the array is generated by the &, ampersand, and the double backslash.
