Calculus, 10th Edition (Anton)

Published by Wiley
ISBN 10: 0-47064-772-8
ISBN 13: 978-0-47064-772-1

Chapter 11 - Three-Dimensional Space; Vectors - 11.5 Parametric Equations Of Lines - Exercises Set 11.5 - Page 811: 36

Answer

On the same line.

Work Step by Step

If $\mathbf{P_1}, \mathbf{P_2}, \mathbf{P_3}$ are points over the same line, vectors $\overrightarrow{\mathbf{P_1P_2}}=\mathbf{u}$ and $\overrightarrow{\mathbf{P_1P_3}}=\mathbf{v}$ are parallel. We have that $$\overrightarrow{\mathbf{P_1P_2}}=\langle 3,-4,-3\rangle-\langle 1,0,1\rangle=\langle 3-1,-4-0,-3-1\rangle=\langle 2,-4,-4\rangle$$ $$\overrightarrow{\mathbf{P_1P_3}}=\langle 4,-6,5\rangle-\langle 1,0,1\rangle=\langle 3,-6,-6\rangle$$ We note that $\overrightarrow{\mathbf{P_1P_2}}=2\langle 1,-2,-2\rangle=\frac{2}{3}\langle 3,-6,-6\rangle=\frac{2}{3}\mathbf{u}$ and $\mathbf{v}=\frac{3}{2}\mathbf{u}$, $\overrightarrow{\mathbf{u}}$ and $\overrightarrow{\mathbf{v}}$ parallel and are over the same line.
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