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: 16



Work Step by Step

1. Express $x$ from the first equation (solve for x). $3x-7y=15\quad/+7y$ $3x=15+7y\qquad/\div 3$ $x=\displaystyle \frac{15+7y}{3}$ 2. Substitute $x$ in the other equation and solve. $3\displaystyle \cdot\frac{15+7y}{3}+7y=15$ $15+7y+7y=15\qquad/-15$ $14y=0\qquad/\div 14$ $y=0$ 3. Back-substitute into the expression of $x$ (step 1). $x=\displaystyle \frac{15+7(0)}{3}=\frac{15}{3}=5$ 4. Write the solution as an ordered pair. Solution set: $\{(5,0)\}$
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