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 - 4.5 Linear Dependence and Linear Independence - Problems - Page 298: 45

Answer

See below

Work Step by Step

Given $\{v_1, v_2\}$ be a linearly independent set in a vector space $V$ $v,w$ are linearly independent if $av+bw=0 \rightarrow \alpha=\beta=0 \forall a,b \in R$ then $av+bw\\ =a(\alpha_1+v_2)+b(v_1+\alpha v_2)\\ =v_1(a\alpha +b)+v_2(a+\alpha b)\\ =0$ Since $v_1,v_2$ are linearly independent, then we have $a \alpha +b=a+\alpha b=0\\ \rightarrow b=-\alpha a$ Substituting: $a+\alpha (-\alpha a)=0\\ \rightarrow a(-\alpha^2+1)=0\\ \rightarrow -a(\alpha +1)(\alpha -1)=0\\ \rightarrow a=0\\ b=0\\ \alpha=\pm 1$ Hence, the vectors $v$ and $w$ are linearly independents when $\alpha \ne \pm 1$ Substituting: $\alpha =1\\ \rightarrow av+bw\\ =(a+b)v_1+(a+b)v_2\\ =(a+b)(v_1+v_2)=0$
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