College Algebra (6th Edition)

Published by Pearson
ISBN 10: 0-32178-228-3
ISBN 13: 978-0-32178-228-1

Chapter 5 - Systems of Equations and Inequalities - Exercise Set 5.2 - Page 538: 26

Answer

$(-3,0,2)$

Work Step by Step

We are given the system: $\begin{cases} \dfrac{x+3}{2}-\dfrac{y-1}{2}+\dfrac{z+2}{4}=\dfrac{3}{2}\\ \dfrac{x-5}{2}+\dfrac{y+1}{3}-\dfrac{z}{4}=-\dfrac{25}{6}\\ \dfrac{x-3}{4}-\dfrac{y+1}{2}+\dfrac{z-3}{2}=-\dfrac{5}{2} \end{cases}$ Multiply the Equation 1 by 4, Equation 2 by 12 and Equation 3 by 4 to eliminate denominators: $\begin{cases} 4\left(\dfrac{x+3}{2}-\dfrac{y-1}{2}+\dfrac{z+2}{4}\right)=4\left(\dfrac{3}{2}\right)\\ 12\left(\dfrac{x-5}{2}+\dfrac{y+1}{3}-\dfrac{z}{4}\right)=12\left(-\dfrac{25}{6}\right)\\ 4\left(\dfrac{x-3}{4}-\dfrac{y+1}{2}+\dfrac{z-3}{2}\right)=4\left(-\dfrac{5}{2}\right) \end{cases}$ $\begin{cases} 2(x+3)-2(y-1)+z+2=2(3)\\ 6(x-5)+4(y+1)-3z=2(-25)\\ x-3-2(y+1)+2(z-3)=2(-5) \end{cases}$ $\begin{cases} 2x+6-2y+2+z+2=6\\ 6x-30+4y+4-3z=-50\\ x-3-2y-2+2z-6=-10 \end{cases}$ $\begin{cases} 2x-2y+z=-4\\ 6x+4y-3z=-24\\ x-2y+2z=1 \end{cases}$ We will use the addition method. Multiply Equation 1 by 2 and add it to Equation 2 to eliminate $y$. Also multiply Equation 1 by -1 and add it to Equation 3 to eliminate $y$: $\begin{cases} 6x+4y-3z+2(2x-2y+z)=-24+2(-4)\\ x-2y+2z+(-1)(2x-2y+z)=1+(-1)(-4) \end{cases}$ $\begin{cases} 6x+4y-3z+4x-4y+2z=-32\\ x-2y+2z-2x+2y-z=5 \end{cases}$ $\begin{cases} 10x-z=-32\\ -x+z=5 \end{cases}$ Add Equation 1 to Equation 2 to eliminate $z$ and determine $x$: $10x-z-x+z=-32+5$ $9x=-27$ $x=-3$ Substitute the value of $x$ in the Equation $-x+z=5$ to determine $z$: $-(-3)+z=5$ $3+z=5$ $z=2$ Substitute the values of $x, z$ is Equation 1 of the given system to find $y$: $2x-2y+z=-4$ $2(-3)-2y+2=-4$ $-4-2y=-4$ $2y=0$ $y=0$ The system's solution is: $(-3,0,2)$
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