## College Algebra (6th Edition)

$\left[\begin{array}{lllll} 1 & 2 & 2 & | & 2\\ 0 & 1 & -1 & | & 2\\ 0 & 0 & 9 & | & -9 \end{array}\right]$
The elements of the third row will be replaced with $0\rightarrow\quad-5(0)+0=0$ $5\rightarrow\quad-5(1)+5=0$ $4\rightarrow\quad-5(-1)+4=9$ $1\rightarrow\quad-5(2)+1=-9$ so the new matrix is $\left[\begin{array}{lllll} 1 & 2 & 2 & | & 2\\ 0 & 1 & -1 & | & 2\\ 0 & 0 & 9 & | & -9 \end{array}\right]$