Differential Equations and Linear Algebra (4th Edition)

Published by Pearson
ISBN 10: 0-32196-467-5
ISBN 13: 978-0-32196-467-0

Chapter 2 - Matrices and Systems of Linear Equations - 2.5 Gaussian Elimination - Problems - Page 166: 21

Answer

The solution set is $(t,1.3)$

Work Step by Step

$Ax=b$ $\begin{bmatrix} 0 & 1 & -1\\ 0& 5 & 1\\ 0 & 2 &1 \end{bmatrix}.\begin{bmatrix} x_1\\ x_2\\ x_3 \end{bmatrix}=\begin{bmatrix} -2\\ 8\\ 5 \end{bmatrix}$ Converting the given system of equations to an augmented matrix and then using Gauss-Jordan elimination to determine the solution set to the given system. $\begin{bmatrix} 0 & 1 & -1|-2\\ 0& 5 & 1|8\\ 0 & 2 &1|5 \end{bmatrix} \approx^1\begin{bmatrix} 0 & 1 & -1|-2\\ 0& 0 & 6|18\\ 0 & 0 &3|9 \end{bmatrix} \approx^2 \begin{bmatrix} 0 & 1 & -1|-2\\ 0& 0 & 1|3\\ 0 & 0 &3|9 \end{bmatrix} \approx^3 \begin{bmatrix} 0 & 1 & -1|-2\\ 0& 0 & 1|3\\ 0 & 0 &0|0 \end{bmatrix}$ 1. $A_{12}(-5),A_{13}(-2)$ 2. $M_2(\frac{1}{6})$ 5. $A_{21}(1),A_{23}(-3)$ The equivalent system is $x_2-x_3=-2$ $x_3=3$ $x_1 = t$ There is one free variable, which we take to be $x_1 = t$, where t can assume any complex value. Applying back substitution yields: $x_3=3$ $x_1 = t$ $x_2-3=-2 \rightarrow x_2=1$ The solution set is $(t,1.3)$
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