\[ \left( \begin{array}{rrrr} 
2.00 & 9.00 & 9.00 & 4.00\\
2.00 & -3.00 & 12.00 & 8.00\\
4.00 & 8.00 & 3.00 & -5.00\\
1.00 & 2.00 & 6.00 & 4.00\\
\end{array} \right)
\left( \begin{array}{c}
x_1 \\x_2 \\x_3 \\x_4 \end{array} \right) = 
\left( \begin{array}{r}
1.00 \\2.00 \\3.00 \\4.00 \end{array} \right) 
\]
