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: 20



Work Step by Step

1. y has opposite signs in the equations. Multiplying the first equation by $2$ will eliminate y. $\left\{\begin{array}{lll} 8x & +2y & =-46\\ x & -2y & =-17 \end{array}\right.$ 2. ... add the equations and solve $9x=-63\qquad/\div 9$ $x=-7$ 3. Back-substitute into one of the initial equations $4x+y=-23$ $4(-7)+y=-23$ $-28+y=-23\qquad/+28$ $y=5$ 4. Write the solution as an ordered pair. Solution set: $\{(-7,5)\}$
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