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 212: 8

Answer

$$\eqalign{ & y{\text{ - intercept }}\left( {0, - \frac{1}{4}} \right) \cr & {\text{No }}x{\text{ - intercept}}{\text{.}} \cr & {\text{Relative maximum at}}\left( {0, - \frac{1}{4}} \right) \cr & {\text{No inflection points}} \cr & {\text{Horizontal asymptote }}y = 1 \cr & {\text{Vertical asymptotes}}{\text{, }}x = 2,{\text{ }}x = - 2 \cr} $$

Work Step by Step

$$\eqalign{ & y = \frac{{{x^2} + 1}}{{{x^2} - 4}} \cr & {\text{Find the }}y{\text{ intercept}}{\text{, let }}x = 0 \cr & y = \frac{{{0^2} + 1}}{{{0^2} - 4}} \cr & y = - \frac{1}{4} \cr & y{\text{ - intercept }}\left( {0, - \frac{1}{4}} \right) \cr & {\text{Find the }}x{\text{ intercept}}{\text{, let }}y = 0 \cr & 0 = \frac{{{x^2} + 1}}{{{x^2} - 4}} \cr & {x^2} + 1 = 0,{\text{ No real solutions }} \cr & {\text{No }}x{\text{ - intercept}}{\text{.}} \cr & \cr & *{\text{Find the extrema}} \cr & {\text{Differentiate}} \cr & y' = \frac{d}{{dx}}\left[ {\frac{{{x^2} + 1}}{{{x^2} - 4}}} \right] \cr & y' = \frac{{\left( {{x^2} - 4} \right)\left( {2x} \right) - \left( {{x^2} + 1} \right)\left( {2x} \right)}}{{{{\left( {{x^2} - 4} \right)}^2}}} \cr & y' = \frac{{2{x^3} - 8x - 2{x^3} - 2x}}{{{{\left( {{x^2} - 4} \right)}^2}}} \cr & y' = \frac{{ - 10x}}{{{{\left( {{x^2} - 4} \right)}^2}}} \cr & {\text{Let }}y' = 0 \cr & \frac{{ - 10x}}{{{{\left( {{x^2} - 4} \right)}^2}}} = 0 \cr & x = 0 \cr & \cr & {\text{Find the second derivative}} \cr & y'' = \frac{d}{{dx}}\left[ {\frac{{ - 10x}}{{{{\left( {{x^2} - 4} \right)}^2}}}} \right] \cr & y'' = \frac{{{{\left( {{x^2} - 4} \right)}^2}\left( { - 10} \right) + 10x\left( 2 \right)\left( {{x^2} - 4} \right)\left( {2x} \right)}}{{{{\left( {{x^2} - 4} \right)}^4}}} \cr & y'' = \frac{{\left( {{x^2} - 4} \right)\left( { - 10} \right) + 10x\left( 2 \right)\left( {2x} \right)}}{{{{\left( {{x^2} - 4} \right)}^3}}} \cr & y'' = \frac{{ - 10{x^2} + 40 + 40{x^2}}}{{{{\left( {{x^2} - 4} \right)}^3}}} \cr & y'' = \frac{{30{x^2} + 40}}{{{{\left( {{x^2} - 4} \right)}^3}}} \cr & {\text{Evaluate }}y''\left( 0 \right) \cr & y''\left( 0 \right) = \frac{{30{{\left( 0 \right)}^2} + 40}}{{{{\left( {{{\left( 0 \right)}^2} - 4} \right)}^3}}} = - \frac{5}{8} < 0 \cr & {\text{Relative maximum at }}\left( {0,f\left( 0 \right)} \right) \to \left( {0, - \frac{1}{4}} \right) \cr & \cr & *{\text{Find the Inflection points}} \cr & y'' = \frac{{30{x^2} + 40}}{{{{\left( {{x^2} - 4} \right)}^3}}} \cr & \frac{{30{x^2} + 40}}{{{{\left( {{x^2} - 4} \right)}^3}}} = 0 \cr & 30{x^2} + 40 = 0,{\text{ No real solutions}} \cr & {\text{No inflection points}} \cr & \cr & {\text{*Calculate the asymptotes}} \cr & y = \frac{{{x^2} + 1}}{{{x^2} - 4}} \cr & {x^2} - 4 = 0,{\text{ }}x = \pm 2 \cr & {\text{Vertical asymptotes}}{\text{, }}x = 2,{\text{ }}x = - 2 \cr & \mathop {\lim }\limits_{x \to \infty } \left( {\frac{{{x^2} + 1}}{{{x^2} - 4}}} \right) = 1 \cr & \mathop {\lim }\limits_{x \to - \infty } \left( {\frac{{{x^2} + 1}}{{{x^2} - 4}}} \right) = 1 \cr & {\text{Horizontal asymptote }}y = 1 \cr & \cr & {\text{Graph}} \cr} $$
Update this answer!

You can help us out by revising, improving and updating this answer.

Update this answer

After you claim an answer you’ll have 24 hours to send in a draft. An editor will review the submission and either publish your submission or provide feedback.