Precalculus: Concepts Through Functions, A Unit Circle Approach to Trigonometry (3rd Edition)

Published by Pearson
ISBN 10: 0-32193-104-1
ISBN 13: 978-0-32193-104-7

Chapter 10 - Systems of Equations and Inequalities - Section 10.1 Systems of Linear Equations: Substitution and Elimination - 10.1 Assess Your Understanding - Page 734: 36

Answer

$x=12$ and $y=6$

Work Step by Step

We need to solve the given system of equations: $\dfrac{1}{3}x - \dfrac{3}{2}y = -5 ...(1)$ and $\dfrac{3}{4}x + \dfrac{1}{3}y=11 ....(2)$ We need to multiply equation (1) by $\dfrac{1}{3}$ and equation (2) by $\dfrac{3}{2}$ $\dfrac{1}{9}x - \dfrac{1}{2}y = -\dfrac{5}{3} ... (3)$ $\dfrac{9}{8}x + \dfrac{1}{2}y = \dfrac{33}{2} ...(4)$ Now, we will add equations (3) and (4). $(\dfrac{1}{9} + \dfrac{9}{8})x = -\dfrac{5}{3} + \dfrac{33}{2} \\ \dfrac{89}{72}x = \dfrac{89}{6} \\ x=12$ Finally, back substitute into equation (2). $\dfrac{1}{3}y = 11 - \dfrac{3}{4}(12) \\ \implies y=6$ Thus, the solutions to the two given equations are: $x=12$ and $y=6$
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