Elementary Algebra

Published by Cengage Learning
ISBN 10: 1285194055
ISBN 13: 978-1-28519-405-9

Chapter 8 - Coordinate Geometry and Linear Systems - 8.6 - Elimination-by-Addition Method - Problem Set 8.6: 40

Answer

$(-6, 20)$

Work Step by Step

In order to solve this problem, we multiply one or both of the equations by a value that will make one of the variables cancel. We multiply the top equation by 9, and we multiply the bottom equation by -4. Then, we add the two equations to obtain: $ \frac{9y}{5} +\frac{12y}{10} = 60 \\ 3y = 60 \\ y =20$ We plug in the given value into the top equation and solve for the other variable: $2/3 x +1/5(20) = 0 \\ 2/3x = -4 \\ x =-6 $
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