University Calculus: Early Transcendentals (3rd Edition)

Published by Pearson
ISBN 10: 0321999584
ISBN 13: 978-0-32199-958-0

Chapter 10 - Section 10.1 - Parametrizations of Plane Curves - Exercises - Page 562: 12

Answer

$y=\displaystyle \frac{2-x}{2x-1},\ \ x\displaystyle \lt \frac{1}{2}.$

Work Step by Step

From the parametric equation for x, x varies from $\displaystyle \frac{-1}{-1-1}=\frac{1}{2}$ to $-\infty$ (as t nears 1). So, the restriction on x is $x\displaystyle \lt \frac{1}{2}.$ Express t in terms of x: $\displaystyle \frac{t}{t-1}=\frac{t-1+1}{t-1}=1+\frac{1}{t-1}$ $x-1=\displaystyle \frac{1}{t-1}$ $t-1=\displaystyle \frac{1}{x-1}$ $t=\displaystyle \frac{1}{x-1}+1=\frac{1+x-1}{1-x}$ $t=\displaystyle \frac{x}{x-1},\quad x\lt \frac{1}{2}.$ Substituting into the parametric equation for y, $y=\displaystyle \frac{\frac{x}{x-1}-2}{\frac{x}{x-1}+1}=\frac{\frac{x-2(x-1)}{x-1}}{\frac{x+x-1}{x-1}}=\frac{2-x}{2x-1}$ Include the restriction $ y=\displaystyle \frac{2-x}{2x-1},\ \ x\displaystyle \lt \frac{1}{2}.$ To graph, create a function value table using values for t, in ascending order of t, calculating the x- and y-coordinates of points on the graph. Plot and join the points obtained with a smooth curve, noting the direction in which t increases.
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