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 - Page 332: 27


The two lines/equations $coincide$ (overlap). Infinite solutions.

Work Step by Step

We use the addition method: We add the 2 equations: $3x-5y=7$ $9x-15y=21$ Multiply both sides of the first equation by $-3$ to cancel $x$. $-9x+15y=-21$ $\underline{+9x-15y=+21}$ $0=0$ This is a true statement, which means that we have infinite solutions. So, the two equations coincide (overlap).
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