Calculus: Early Transcendentals (2nd Edition)

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

Chapter 6 - Applications of Integration - 6.8 Logarithmic and Exponential - 6.8 Exercises: 21

Answer

$$4 - \frac{4}{{{e^2}}}$$

Work Step by Step

$$\eqalign{ & \int_0^2 {4x{e^{ - {x^2}/2}}} dx \cr & {\text{substitute }}u = - {x^2}/2,{\text{ }}du = - xdx \cr & {\text{express the limits in terms of }}u \cr & x = 2{\text{ implies }}u = - {\left( 2 \right)^2}/2 = - 2 \cr & x = 0{\text{ implies }}u = - {\left( 0 \right)^2}/2 = 0 \cr & {\text{the entire integration is carried out as follows}} \cr & \int_0^2 {4x{e^{ - {x^2}/2}}} dx = - 4\int_0^{ - 2} {{e^u}} du \cr & {\text{find the antiderivative}} \cr & = - 4\left. {{e^u}} \right|_0^{ - 2} \cr & {\text{use the fundamental theorem}} \cr & = - 4\left( {{e^{ - 2}} - {e^0}} \right) \cr & {\text{simplify}} \cr & = 4 - \frac{4}{{{e^2}}} \cr} $$
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