Intermediate Algebra (6th Edition)

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

Chapter 4 - Section 4.2 - Solving Systems of Linear Equations in Three Variables - Exercise Set - Page 220: 23

Answer

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

Work Step by Step

$2x+2y-3z=1$ Equation $(1)$ $y+2z=-14$ Equation $(2)$ $3x-2y=-1$ Equation $(3)$ Equation $(1)$ + Equation $(3)$ $(2x+2y-3z)+(3x-2y)=1+(-1)$ $5x-3z=0$ Equation $(4)$ $2\times$Equation $(2)$ - Equation $(1)$ $2(y+2z)-(2x+2y-3z)=2(-14)-1$ $(2y+4z)-(2x+2y-3z)=-28-1$ $-2x+7z=-29$ Equation $(5)$ $(2 \times$ Equation $(4))$ + $(5 \times$ Equation $(5))$ $2(5x-3z)+5(-2x+7z)=2(0)+5(-29)$ $(10x-6z)+(-10x+35z)=-145$ $29z=-145$ $z=-5$ Substitute $z=-5$ into Equation $(4)$ to get $x$. $5x-3(-5)=0$ $5x+15=0$ $5x=-15$ $x=-3$ Substitute $x=-3$ into Equation $(3)$ to get $y$. $3(-3)-2y=-1$ $-9-2y=-1$ $-2y=8$ $y=-4$ $(-3,-4,-5)$ satisfies the given equations. Solution is $(-3,-4,-5)$
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