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: 25

Answer

$\{(2,-2)\}$

Work Step by Step

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: $\{(2,-2)\}$
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