Differential Equations and Linear Algebra (4th Edition)

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

Chapter 4 - Vector Spaces - 4.11 Chapter Review - Additional Problems - Page 336: 26

Answer

See below

Work Step by Step

Given: $V=R^4\\ S=\{(6,-3,2,0),(1,1,1,0),(1,-8,-1,0)\}$ We have $dim(R^4)=4$ but we can see $S$ just have 3 vectors. Thus $S$ do not span $R^4$ Obtain: $a(6,-3,2,0)+b(1,1,1,0)+c(1,-8,-1,0)=0$ $\rightarrow 6a+b+c=0\\ -3a+b-8c=0\\ 2a+b-c=0$ From $6a+b+c=0 \rightarrow a=-\frac{a+b}{6}$ Substitute: $-3(-\frac{a+b}{6})+c-8c=0\\ 2(-\frac{a+b}{6})+b-c=0\\ \rightarrow \frac{3b-15c}{2}=0\\ \frac{2b-4c}{3}=0\\ \rightarrow b=5c\\ \frac{2b-4c}{3}=0$ Substitute: $\frac{2.5c-4c}{3}=0 \rightarrow 2c =0 \rightarrow c=0$ then $a=0\\ b=0$ We have $rank\begin{bmatrix} 6 & -3 & 2 & 0\\ 1 & 1 & 1 &0\\ 1 & -8 & -1 & 0 \end{bmatrix}=3\\ \rightarrow rank(A)=dim(S)=3$ Consequently, the given set of vectors $S$ are linearly independent.
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