Precalculus (6th Edition)

Published by Pearson
ISBN 10: 013421742X
ISBN 13: 978-0-13421-742-0

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



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: $\{(0,4)\}$
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