# Chapter 9 - Systems and Matrices - 9.1 Systems of Linear Equations - 9.1 Exercises - Page 856: 19

$\{(0,4)\}$

#### Work Step by Step

1. y has opposite signs in the equations. Multiplying the first equation by 3 will eliminate y. $\left\{\begin{array}{lll} 9x & -3y & =-12\\ x & +3y & =12 \end{array}\right.$ 2. ... add the equations and solve $10x=0$ $x=0$ 3. Back-substitute into one of the initial equations $x+3y=12$ $0+3y=12$ $3y=12\qquad/\div 3$ $y=4$ 4. Write the solution as an ordered pair. Solution set: $\{(0,4)\}$

After you claim an answer you’ll have 24 hours to send in a draft. An editor will review the submission and either publish your submission or provide feedback.