Answer
u is in the subspace of $R^4$ generated by ${v_1,v_2,v_3}$
Work Step by Step
$\begin{bmatrix}
1&4&5&-4\\
-2&-7&-8&10\\
4&9&6&-7\\
3&7&5&-5
\end{bmatrix}
$~$\begin{bmatrix}
1&0&-3&0\\
0&1&2&0\\
0&0&0&1\\
0&0&0&0
\end{bmatrix}
$, which means u is in the subspace of $R^4$ generated by ${v_1,v_2,v_3}$
