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: 15

Answer

The solution is $(2t-3,t,t)$

Work Step by Step

The augmented matrix of the system is: $\begin{bmatrix} 1&0 &-2 |-3\\ 3 &-2 &-4| -9\\ 1& -4 & 2 |-3 \end{bmatrix}$ with reduced row-echelon form: $\begin{bmatrix} 1&0 &-2 |-3\\ 3 &-2 &-4| -9\\ 1& -4 & 2 |-3 \end{bmatrix} \approx^1 \begin{bmatrix} 1&0 &-2 |-3\\ 0 &-2 &2| 0\\ 0& -4 & 4 |0 \end{bmatrix} \approx^2 \begin{bmatrix} 1&0 &-2 |-3\\ 0 &1 &-1| 0\\ 0& -4 & 4 |0 \end{bmatrix} \approx^3 \begin{bmatrix} 1&0 &-2 |-3\\ 0 &1 &-1| 0\\ 0& 0 & 0 |0 \end{bmatrix}$ $1.A_{12}(-3), A_{13}(-1)$ $2.M_2(-\frac{1}{2})$ $3.A_{23}(4)$ This matrix is now in row-echelon form. The equivalent system is: $x_1-2x_3=-3$ $x_2-x_3=0$ $x_3=t$ There is one free variable, which we take to be $x_3 = t$, where t can assume any complex value. Applying back substitution yields: $x_3=t$ $x_1-2t=-3 \rightarrow x_1=2t-3$ $x_2-t=0 \rightarrow x_2=t$ The solution is $(2t-3,t,t)$
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