Precalculus (6th Edition)

Published by Pearson
ISBN 10: 013421742X
ISBN 13: 978-0-13421-742-0

Chapter 8 - Application of Trigonometry - 8.4 Algebraically Defined Vectors and the Dot Product - 8.4 Exercises - Page 790: 31

Answer

$$\left. a \right) - 2{\bf{i}} + 4{\bf{j}},\,\,\,\,\,\left. b \right){\bf{i}} + {\bf{j}},\,\,\,\,\,\left. c \right)4{\bf{i}} - 7{\bf{j}}$$

Work Step by Step

$$\eqalign{ & {\text{Let }}{\bf{u}} = - {\bf{i}} + 2{\bf{j}}{\text{ and }}{\bf{v}} = {\bf{i}} - {\bf{j}} \cr & \left. a \right){\text{Find 2}}{\bf{u}} \cr & 2{\bf{u}} = 2\left( { - {\bf{i}} + 2{\bf{j}}} \right) \cr & 2{\bf{u}} = - 2{\bf{i}} + 4{\bf{j}} \cr & \cr & \left. b \right){\text{Find 2}}{\bf{u}} + 3{\bf{v}} \cr & {\text{2}}{\bf{u}} + 3{\bf{v}} = {\text{2}}\left( { - {\bf{i}} + 2{\bf{j}}} \right) + 3\left( {{\bf{i}} - {\bf{j}}} \right) \cr & {\text{2}}{\bf{u}} + 3{\bf{v}} = - 2{\bf{i}} + 4{\bf{j}} + 3{\bf{i}} - 3{\bf{j}} \cr & {\text{2}}{\bf{u}} + 3{\bf{v}} = {\bf{i}} + {\bf{j}} \cr & \cr & \left. c \right){\text{Find }}{\bf{v}} - 3{\bf{u}} \cr & {\bf{v}} - 3{\bf{u}} = {\bf{i}} - {\bf{j}} - 3\left( { - {\bf{i}} + 2{\bf{j}}} \right) \cr & {\bf{v}} - 3{\bf{u}} = {\bf{i}} - {\bf{j}} + 3{\bf{i}} - 6{\bf{j}} \cr & {\bf{v}} - 3{\bf{u}} = 4{\bf{i}} - 7{\bf{j}} \cr} $$
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