University Calculus: Early Transcendentals (3rd Edition)

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

Chapter 8 - Section 8.1 - Integration by Parts - Exercises - Page 427: 17

Answer

$$\int (x^2-5x)e^xdx=e^x(x^2-7x+7)+C$$

Work Step by Step

$$A=\int (x^2-5x)e^xdx$$ Set $u=x^2-5x$ and $dv=e^xdx$ Then we have $du=(2x-5)dx$ and $v=e^x$ Using the formula $\int udv= uv-\int vdu$: $$A=(x^2-5x)e^x-\int(2x-5)e^xdx$$ Set $u=2x-5$ and $dv=e^xdx$ Then we have $du=2dx$ and $v=e^x$ Using the formula $\int udv= uv-\int vdu$: $$A=(x^2-5x)e^x-\Big((2x-5)e^x-2\int e^xdx\Big)$$ $$A=(x^2-5x)e^x-(2x-5)e^x+2e^x+C$$ $$A=e^x(x^2-5x-2x+5+2)+C$$ $$A=e^x(x^2-7x+7)+C$$
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