## Intermediate Algebra for College Students (7th Edition)

The answer is $\left[\begin{array}{ccc|c} 1& 2 & 1&2 \\ 0&3 &4&9 \\ 0&1&-3&- 10\\ \end{array}\right]$.
The given matrix is $\left[\begin{array}{ccc|c} 1& 2 & 1&2 \\ -2 &-1 &2&5 \\ 1&3&-2&-8\\ \end{array}\right]$ Perform $2R_1+R_2$ and $-1R_1+R_3$. Multiply row one by $2$ and add to row two. Multiply row one by $-1$ and add to row three. $\left[\begin{array}{ccc|c} 1& 2 & 1&2 \\ 2\cdot 1-2 &2\cdot 2-1 &2\cdot 1+2&2\cdot 2+5 \\ -1\cdot 1+1&-1\cdot 2+3&-1\cdot 1-2&-1\cdot 2-8\\ \end{array}\right]$ Simplify. $\left[\begin{array}{ccc|c} 1& 2 & 1&2 \\ 2-2 &4-1 &2+2&4+5 \\ -1+1&- 2+3&-1-2&- 2-8\\ \end{array}\right]$ $\left[\begin{array}{ccc|c} 1& 2 & 1&2 \\ 0&3 &4&9 \\ 0&1&-3&- 10\\ \end{array}\right]$.