Precalculus (6th Edition) Blitzer

Published by Pearson
ISBN 10: 0-13446-914-3
ISBN 13: 978-0-13446-914-0

Chapter 6 - Section 6.6 - Vectors - Exercise Set - Page 782: 33

Answer

$-5\mathbf{i}+45\mathbf{j}$

Work Step by Step

Therefore, the value of $3\mathbf{v},4\mathbf{w}$ is, $\begin{align} & 3\mathbf{v}=\left[ 3\times \left( -3 \right) \right]\mathbf{i}+\left[ 3\times 7 \right]\mathbf{j} \\ & =-9\mathbf{i}+21\mathbf{j} \end{align}$ $\begin{align} & 4\mathbf{w}=\left[ 4\times \left( -1 \right) \right]\mathbf{i}+\left[ 4\times \left( -6 \right) \right]\mathbf{j} \\ & =-4\mathbf{i}-24\mathbf{j} \end{align}$ Subtract $4\mathbf{w}$ from $3\mathbf{v}$ to get, $\begin{align} & 3\mathbf{v}-4\mathbf{w}=\left[ -9-\left( -4 \right) \right]\mathbf{i}+\left[ 21-\left( -24 \right) \right]\mathbf{j} \\ & =-5\mathbf{i}+45\mathbf{j} \end{align}$
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