Algebra: A Combined Approach (4th Edition)

Published by Pearson
ISBN 10: 0321726391
ISBN 13: 978-0-32172-639-1

Chapter 4 - Test - Page 330: 13

Answer

$$x=4$$ $$y=-5$$

Work Step by Step

Equation 1: $3x + y = 7$ Equation 2: $4x + 3y = 1$ Multiply equation 1 by $-3$: $$[3x + y = 7]\cdot-3$$ $$-9x -3y =-21$$ Add this equation to equation 2: $$-9x -3y =-21$$ $$+$$ $$4x + 3y = 1$$ $$=$$ $$-5x=-20$$ Divide both sides by $-5$: $$\frac{-5x}{-5}=\frac{-20}{-5}$$ $$x=4$$ Substitute this value of $x$ to equation 1: $$3x + y = 7$$ $$3(4) + y = 7$$ $$12 + y = 7$$ Subtract $12$ from both sides: $$12 -12+ y = 7-12$$ $$y=-5$$ Use equation 2 to check: $$4x + 3y = 1$$ $$4(4) + 3(-5) = 1$$ $$16 -15 = 1$$ $$1=1$$
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