Find two linearly independent vectors (u,v) that spans the same subspace  R^4 as that spanned by the vectors

\begin{bmatrix} 0\\3\\3\\1 \end{bmatrix} , \begin{bmatrix} 3\\-1\\-2\\1 \end{bmatrix}, \begin{bmatrix} 3\\8\\7\\4 \end{bmatrix} , \begin{bmatrix} -9\\6\\9\\-2 \end{bmatrix}

What I did already was reduced the augmented matrix:

 \begin{bmatrix} 0&3&3&-9&0 \\ 3&-1&8&6&0 \\3&-2&7&9&0 \\1&1&4&-2&0 \end{bmatrix}

into:

 \begin{bmatrix}  1&0&3&1&0 \\ 0&1&1&-3&0 \\0&0&0&0&0 \\ 0&0&0&0&0 \end{bmatrix}

This means that  x_1 = -3x_3 -x_4
 x_2 =-x_3 +3x_4 and  x_3 , x_4 being free

Where I go from here?