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 - 11.2 Systems of Linear Equations: Matrices - 11.2 Assess Your Understanding - Page 731: 59

Answer

Consistent Solution set: $\{(1,3,-2)\}$

Work Step by Step

We are given the system of equations: $\begin{cases} x+y-z=6\\ 3x-2y+z=-5\\ x+3y-2z=14 \end{cases}$ Write the augmented matrix: $\begin{bmatrix} 1&1&-1&|&6\\3&-2&1&|&-5\\1&3&-2&|&14\end{bmatrix}$ Perform row operations to bring the matrix to the reduced row echelon form: $R_2=-3r_1+r_2$ $\begin{bmatrix} 1&1&-1&|&6\\0&-5&4&|&-23\\1&3&-2&|&14\end{bmatrix}$ $R_3=-r_1+r_3$ $\begin{bmatrix}1&1&-1&|&6\\0&-5&4&|&-23\\0&2&-1&|&8\end{bmatrix}$ $R_2=2r_3+r_2$ $\begin{bmatrix}1&1&-1&|&6\\0&-1&2&|&-7\\0&2&-1&|&8\end{bmatrix}$ $R_2=-r_2$ $\begin{bmatrix}1&1&-1&|&6\\0&1&-2&|&7\\0&2&-1&|&8\end{bmatrix}$ $R_3=-2r_2+r_3$ $\begin{bmatrix}1&1&-1&|&6\\0&1&-2&|&7\\0&0&3&|&-6\end{bmatrix}$ $R_3=\dfrac{1}{3}r_3$ $\begin{bmatrix}1&1&-1&|&6\\0&1&-2&|&7\\0&0&1&|&-2\end{bmatrix}$ Write the corresponding system of equations: $\begin{cases} x+y-z=6\\ y-2z=7\\ z=-2 \end{cases}$ Solve the system by back substitution: $z=-2$ $y-2z=7$ $y-2(-2)=7$ $y=3$ $x+y-z=6$ $x+3-(-2)=6$ $x+5=6$ $x=1$ The solution is: $\{(1,3,-2)\}$
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