## Precalculus (10th Edition)

$\left[\begin{array}{rrr|r} 4&-5&1&0 \\ -2 & -1 & 0 & -25 \\ 1&5&-5&10 \\ \end{array} \right]$
Write the second and third equations in the right form: $-2x-y+6=-19\\-2x-y=-25$ We know that $\left\{ \begin{array}{c} a_1x+b_1y+c_1z=d_1 \\ a_2x+b_2y+c_2z=d_2 \\ a_3x+b_3y+c_3z=d_3 \\ \end{array} \right.$ becomes $\left[\begin{array}{rrr|r} a_1 & b_1 & c_1 & d_1 \\ a_2 & b_2 & c_2 & d_2 \\ a_3 & b_3 & c_3 & d_3 \\ \end{array} \right]$ Hence here the augmented matrix is: $\left[\begin{array}{rrr|r} 4&-5&1&0 \\ -2 & -1 & 0 & -25 \\ 1&5&-5&10 \\ \end{array} \right]$