Calculus (3rd Edition)

Published by W. H. Freeman
ISBN 10: 1464125260
ISBN 13: 978-1-46412-526-3

Chapter 16 - Multiple Integration - 16.6 Change of Variables - Exercises - Page 904: 6

Answer

The image of the line through the points $\left( {u,v} \right) = \left( {1,1} \right)$ and $\left( {u,v} \right) = \left( {1, - 1} \right)$ is the line through the points $\left( {3,8} \right)$ and $\left( {1,2} \right)$ in the $xy$-plane. The equation of the line is $y=3x-1$.

Work Step by Step

We have the mapping $G\left( {u,v} \right) = \left( {2u + v,5u + 3v} \right)$. The image of the point $\left( {u,v} \right) = \left( {1,1} \right)$ is $G\left( {1,1} \right) = \left( {3,8} \right)$. The image of the point $\left( {u,v} \right) = \left( {1, - 1} \right)$ is $G\left( {1, - 1} \right) = \left( {1,2} \right)$. Since $G$ is a linear map, the image of a line in $uv$-plane is a line in the $xy$-plane. So, the image of the line through the points $\left( {u,v} \right) = \left( {1,1} \right)$ and $\left( {u,v} \right) = \left( {1, - 1} \right)$ is the line through the points $\left( {3,8} \right)$ and $\left( {1,2} \right)$ in the $xy$-plane. Next, we find the line equation in slope-intercept form in the $xy$-plane. The slope is $\frac{{2 - 8}}{{1 - 3}} = 3$. So, the equation of the line: $y-8=3 (x-3)$ $y=3x-1$
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