Calculus 10th Edition

Published by Brooks Cole
ISBN 10: 1-28505-709-0
ISBN 13: 978-1-28505-709-5

Chapter 3 - Applications of Differentiation - 3.6 Exercises - Page 213: 57

Answer

$f\left( x \right) = \frac{{3{x^2} - 7x - 5}}{{x - 3}}$

Work Step by Step

$$\eqalign{ & {\text{Vertical asymptote: }}x = 3 \cr & {\text{To obtain a vertical asymptote at }}x = 3,{\text{ set in the}} \cr & {\text{denominator of the rational function an expression}} \cr & {\text{whose real root is }}x = 3,{\text{ then using }}x - 3 \cr & f\left( x \right) = \frac{1}{{x - 3}} \cr & {\text{Slant asymptote: }}y = 3x + 2 \cr & {\text{To obtain a slant asymptote }}y = 3x + 2, \cr & {\text{the long division the of the rational function }} \cr & f\left( x \right) = \frac{{P\left( x \right)}}{{Q\left( x \right)}}{\text{ must be:}} \cr & {\text{ }}f\left( x \right) = 3x + 2 + \frac{c}{{Q\left( x \right)}},{\text{ where }}c{\text{ is any constant }} \ne {\text{0}} \cr & \cr & {\text{Let }}Q\left( x \right) = x - 3,{\text{ then}} \cr & \frac{{P\left( x \right)}}{{Q\left( x \right)}} = 3x + 2 + \frac{c}{{Q\left( x \right)}} \cr & \frac{{P\left( x \right)}}{{x - 3}} = 3x + 2 + \frac{c}{{x - 3}} \cr & \frac{{P\left( x \right)}}{{x - 3}} = 3x + 2 + \frac{c}{{x - 3}} \cr & \cr & {\text{Solving for }}P\left( x \right) \cr & P\left( x \right) = \left( {3x + 2} \right)\left( {x - 3} \right) + c \cr & P\left( x \right) = 3{x^2} - 9x + 2x - 6 + c \cr & P\left( x \right) = 3{x^2} - 7x - 6 + c \cr & {\text{Let }}c = 1 \cr & P\left( x \right) = 3{x^2} - 7x - 5 \cr & \cr & {\text{Therefore}}{\text{,}} \cr & f\left( x \right) = \frac{{3{x^2} - 7x - 5}}{{x - 3}} \cr} $$
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