The question states determine whether the given matrix is invertible. If it is calculate the inverse:

$\displaystyle \begin{pmatrix} 1 & 1 & 1 & 1 \\1 & 2 & -1 & 2 \\1 & -1 & 2 & 1 \\1 & 3 & 3 & 2 \end{pmatrix}$

Ive tried it many times, but cant seem to get anywhere near what i should be getting.. Can anyone help?