Elementary Technical Mathematics

Published by Brooks Cole
ISBN 10: 1285199197
ISBN 13: 978-1-28519-919-1

Chapter 9 - Section 9.2 - Solving Pairs of Linear Equations by Addition - Exercises: 9

Answer

(-5,5)

Work Step by Step

Add the 2 equations. $\ \ 2x+5y=15$ multiply both sides by -1 $\underline{\ \ 7x+5y=-10}$ $\ \ -2x-5y=-15$ $\underline{\ \ \ \ \ \ \ 7x+5y=-10}$ $\ \ \ \ \ \ \ 5x\ \ \ \ \ \ \ \ \ =-25$ divide both sides by 5 $\ \ \ \ \ \ \ \ \ x\ \ \ \ \ \ \ \ \ =\ -5$ Substitute and solve for y. $2x+5y=15$ $2(-5)+5y=15$ $-10+5y=15$ $-10+5y+10=15+10$ $5y=25$ $5y\div5=25\div5$ $y=5$
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