Precalculus (10th Edition)

Published by Pearson
ISBN 10: 0-32197-907-9
ISBN 13: 978-0-32197-907-0

Chapter 11 - Systems of Equations and Inequalities - 11.1 Systems of Linear Equations: Substitution and Elimination - 11.1 Assess Your Understanding - Page 715: 45

Answer

$\left\{\left(2,-1,1\right)\right\}$

Work Step by Step

We are given the system of equations: $\begin{cases} x-2y+3z=7\\ 2x+y+z=4\\ -3x+2y-2z=-10 \end{cases}$ Use the elimination method. Multiply the first equation by -2 and add it to the second equation to eliminate $x$. Multiply the first equation by 3 and add it to the third equation to eliminate $x$. $\begin{cases} 2x+y+z-2(x-2y+3z)=4-2(7)\\ -3x+2y-2z+3(x-2y+3z)=-10+3(7) \end{cases}$ $\begin{cases} 2x+y+z-2x+4y-6z=-10\\ -3x+2y-2z+3x-6y+9z=11 \end{cases}$ $\begin{cases} 5y-5z=-10\\ -4y+7z=11 \end{cases}$ $\begin{cases} y-z=-2\\ -4y+7z=11 \end{cases}$ Multiply the first equation by 4 and add it to the second equation to eliminate $y$ and determine $z$: $\begin{cases} 4y-4z=4(-2)\\ -4y+7z=11 \end{cases}$ $4y-4z-4y+7z=-8+11$ $3z=3$ $z=1$ Determine $y$: $y-z=-2$ $y-1=-2$ $y=-1$ Determine $x$: $x-2y+3z=7$ $x-2(-1)+3(1)=7$ $x+5=7$ $x=2$ The solution set of the system is: $\left\{\left(2,-1,1\right)\right\}$
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