## Precalculus (6th Edition)

$\{(2,-2)\}$
1. y has opposite signs in the equations. Multiply the first equation with 6, the second with 7, which will lead to eliminating y: $\left\{\begin{array}{llll} 36x & +42y & +12 & =0\\ 49x & -42y & -182 & =0 \end{array}\right.$ 2. ... add the equations and solve $85x-170=0\qquad/+170$ $85x=170\qquad/\div 85$ $x=2$ 3. Back-substitute into one of the initial equations $6x+7y+2=0$ $6(2)+7y+2=0$ $7y+14=0\qquad/-14$ $7y=-14\qquad/\div 7$ $y=-2$ 4. Write the solution as an ordered pair. Solution set: $\{(2,-2)\}$