Calculus: Early Transcendentals (2nd Edition)

Published by Pearson
ISBN 10: 0321947347
ISBN 13: 978-0-32194-734-5

Chapter 7 - Integration Techniques - Review Exercises - Page 595: 94

Answer

$$y = {e^{\sqrt {2{t^2} - 7} }}$$

Work Step by Step

$$\eqalign{ & \frac{{dy}}{{dt}} = \frac{{2ty}}{{\ln y}},\,\,\,\,\,\,y\left( 2 \right) = e \cr & {\text{Separate the variables}} \cr & \frac{{\ln y}}{y}dy = 2tdt \cr & {\text{Integrating}} \cr & \int {\frac{{\ln y}}{y}} dy = \int {2t} dt \cr & \frac{{{{\left( {\ln y} \right)}^2}}}{2} = {t^2} + C \cr & {\text{Use the initial condition }}\,y\left( 2 \right) = e \cr & \frac{{{{\left( {\ln e} \right)}^2}}}{2} = {2^2} + C \cr & \frac{1}{2} = 4 + C \cr & C = - \frac{7}{2} \cr & ,{\text{ then}} \cr & \frac{{{{\left( {\ln y} \right)}^2}}}{2} = {t^2} - \frac{7}{2} \cr & {\text{Solve for }}y \cr & {\left( {\ln y} \right)^2} = 2{t^2} - 7 \cr & \ln y = \sqrt {2{t^2} - 7} \cr & y = {e^{\sqrt {2{t^2} - 7} }} \cr} $$
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