mathURL
http://mathurl.com/7hoegjb
<img src="http://mathurl.com/7hoegjb.png" />
![\left[ \begin{array}{cccc} 1 & 0 & 0 \\ 0 & 1 & 0 \\ 0 & 0 & 1 \end{array} \right]\left[ \begin{array}{cccc} x \\ y \\ 1 \end{array} \right]](http://mathurl.com/7hoegjb.png)