College Algebra (6th Edition)

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

Chapter 6 - Summary, Review, and Test - Review Exercises - Page 655: 5

Answer

$x_1=2$ $x_2=-2$ $x_3=3$ $x_4=4$

Work Step by Step

Build the augmented matrix of the system of equations; $\begin{bmatrix}3&5&-8&5&|&-8\\1&2&-3&1&|&-7\\2&3&-7&3&|&-11\\4&8&-10&7&|&-10\end{bmatrix}$ Bring the matrix to the row reduced echelon form: Switch $R_1$ and $R_2$: $\begin{bmatrix}1&2&-3&1&|&-7\\3&5&-8&5&|&-8\\2&3&-7&3&|&-11\\4&8&-10&7&|&-10\end{bmatrix}$ Add $-3R_1$ to $R_2$, $-2R_1$ to $R_3$ and $-4R_1$ to $R_4$: $\begin{bmatrix}1&2&-3&1&|&-7\\0&-1&1&2&|&13\\0&-1&-1&1&|&3\\0&0&2&3&|&18\end{bmatrix}$ Multiply $R_2$ by -1, then add it to $R_3$: $\begin{bmatrix}1&2&-3&1&|&-7\\0&1&-1&-2&|&-13\\0&-1&-1&1&|&3\\0&0&2&3&|&18\end{bmatrix}$ $\begin{bmatrix}1&2&-3&1&|&-7\\0&1&-1&-2&|&-13\\0&0&-2&-1&|&-10\\0&0&2&3&|&18\end{bmatrix}$ Add $-2R_2$ to $R_1$: $\begin{bmatrix}1&0&-1&5&|&19\\0&1&-1&-2&|&-13\\0&0&-2&-1&|&-10\\0&0&2&3&|&18\end{bmatrix}$ Add $R_3$ to $R_4$: $\begin{bmatrix}1&0&-1&5&|&19\\0&1&-1&-2&|&-13\\0&0&-2&-1&|&-10\\0&0&0&2&|&8\end{bmatrix}$ Multiply $R_4$ to $0.5$: $\begin{bmatrix}1&0&-1&5&|&19\\0&1&-1&-2&|&-13\\0&0&-2&-1&|&-10\\0&0&0&1&|&4\end{bmatrix}$ Multiply $R_3$ to $-0.5$: $\begin{bmatrix}1&0&-1&5&|&19\\0&1&-1&-2&|&-13\\0&0&1&0.5&|&5\\0&0&0&1&|&4\end{bmatrix}$ Add $R_3$ to $R_1$ and $R_2$: $\begin{bmatrix}1&0&0&5.5&|&24\\0&1&0&-1.5&|&-8\\0&0&1&0.5&|&5\\0&0&0&1&|&4\end{bmatrix}$ Add $-5.5R_4$ to $R_1$: $\begin{bmatrix}1&0&0&0&|&2\\0&1&0&-1.5&|&-8\\0&0&1&0.5&|&5\\0&0&0&1&|&4\end{bmatrix}$ Add $1.5R_4$ to $R_2$: $\begin{bmatrix}1&0&0&0&|&2\\0&1&0&0&|&-2\\0&0&1&0.5&|&5\\0&0&0&1&|&4\end{bmatrix}$ Add $-0.5R_4$ to $R_3$: $\begin{bmatrix}1&0&0&0&|&2\\0&1&0&0&|&-2\\0&0&1&0&|&3\\0&0&0&1&|&4\end{bmatrix}$ The solution is: $x_1=2$ $x_2=-2$ $x_3=3$ $x_4=4$
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