Linear Algebra and Its Applications (5th Edition)

Published by Pearson
ISBN 10: 032198238X
ISBN 13: 978-0-32198-238-4

Chapter 1 - Linear Equations in Linear Algebra - 1.6 Exercises - Page 55: 12

Answer

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Work Step by Step

Intersection Flow in Flow out \[ \begin{array}{lccc} A & x_{1} & = & x_{3}+x_{4}+40 \\ B & 200 & = & x_{1}+x_{2} \\ C & x_{2}+x_{3} & = & x_{5}+100 \\ D & x_{4}+x_{5} & = & 60 \end{array} \] Total Flow $200=200$ Write the equations for each node: \[ \begin{aligned} x_{1} &-x_{3}-x_{4} & &=40 \\ x_{1}+x_{2} & & &=200 \\ & x_{2}+x_{3} & &-x_{5}=100 \\ & & x_{4}+x_{5} &=60 \end{aligned} \] Rearrange the equations: \[ \left[\begin{array}{cccccc} 1 & 0 & -1 & -1 & 0 & 40 \\ 1 & 1 & 0 & 0 & 0 & 200 \\ 0 & 1 & 1 & 0 & -1 & 100 \\ 0 & 0 & 0 & 1 & 1 & 60 \end{array}\right] \] Augmented Matrix \begin{aligned} &\left[\begin{array}{cccccc} 1 & 0 & -1 & -1 & 0 & 40 \\ 0 & 1 & 1 & 1 & 0 & 160 \\ 0 & 1 & 1 & 0 & -1 & 100 \\ 0 & 0 & 0 & 1 & 1 & 60 \end{array}\right]\\ &R_{2}=R_{2}-R_{1}\\ &\left[\begin{array}{cccccc} 1 & 0 & -1 & -1 & 0 & 40 \\ 0 & 1 & 1 & 1 & 0 & 160 \\ 0 & 0 & 0 & -1 & -1 & -60 \\ 0 & 0 & 0 & 1 & 1 & 60 \end{array}\right]\\ &R_{3}=R_{3}-R_{2}\\ &\left[\begin{array}{cccccc} 1 & 0 & -1 & -1 & 0 & 40 \\ 0 & 1 & 1 & 1 & 0 & 160 \\ 0 & 0 & 0 & -1 & -1 & -60 \\ 0 & 0 & 0 & 0 & 0 & 0 \end{array}\right]\\ &R_{4}=R_{4}+R_{3} \end{aligned} \[ \left[\begin{array}{cccccc} 1 & 0 & -1 & -1 & 0 & 40 \\ 0 & 1 & 1 & 1 & 0 & 160 \\ 0 & 0 & 0 & 1 & 1 & 60 \\ 0 & 0 & 0 & 0 & 0 & 0 \end{array}\right] \] The general solution
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