Intermediate Algebra (6th Edition)

Published by Pearson
ISBN 10: 0321785045
ISBN 13: 978-0-32178-504-6

Chapter 5 - Cumulative Review - Page 333: 30

Answer

$(-3,-4,-5)$

Work Step by Step

$x+y-\frac{3}{2}z=\frac{1}{2}$ Equation $(1)$ $-y-2z=14 $ Equation $(2)$ $x-\frac{2}{3}y=-\frac{1}{3}$ Equation $(3)$ Multiply both sides of Equation $(1)$ by $2$ and Equation $(3)$ by $3$ to eliminate fractions, we get $2x+2y-3z = 1$ Equation $(4)$ $-y-2z=14 $ Equation $(5)$ $3x-2y=-1$ Equation $(6)$ Adding Equation $(4)$ and Equation $(6)$ $2x+3x+2y-2y-3z = 1-1$ $5x-3z = 0$ Equation $(7)$ Multiply Equation $(5)$ by $-2$ then add with Equation $(6)$ $-2(-y-2z) + 3x-2y = -2(14)-1$ $2y+4z + 3x -2y = -28 -1$ $3x+4z = -29$ Equation $(8)$ Multiply Equation $(7)$ by $4$ and Equation $(8)$ by $3$ then add $4(5x-3z)+ 3(3x+4z) = 0 +3(-29)$ $20x-12z+9x+12z = -87$ $29x = -87$ $x = -3$ Substituting $x$ value in Equation $(6)$ $3x-2y=-1$ $3(-3)-2y = -1$ $-9-2y = -1$ $-2y = 8$ $y= -4$ Substituting $y$ value in Equation $(5)$ $-y-2z=14 $ $-(-4)-2z = 14$ $4-2z = 14$ $-2z = 10$ $z = -5$ Solution: $(-3,-4,-5)$
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