Linear Algebra and Its Applications (5th Edition)

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

Chapter 4 - Vector Spaces - 4.2 Exercises - Page 208: 27

Answer

$x_{1}=30,\ x_{2}=20,\ x_{3}=-10$ is also a solution to the given system of equations.

Work Step by Step

Let $A$ be the coefficient matrix of the given system of equations. $\mathrm{x}=\left[\begin{array}{l} 3\\ 2\\ -1 \end{array}\right]$ is a solution to $Ax=0$. This means that $\mathrm{x} \in$ Nul A. Nul A is a subspace of $\mathbb{R}^{3}$, so (a) it contains 0, (b) it is closed under addition, and most importantly, (c) it is closed under scalar multiplication. $\left[\begin{array}{l} 30\\ 20\\ -10 \end{array}\right]=10x\in$ Nul A, meaning A$\left[\begin{array}{l} 30\\ 20\\ -10 \end{array}\right]$=0 So $x_{1}=30,\ x_{2}=20,\ x_{3}=-10$ is also a solution to the given system of equations.
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