Calculus 8th Edition

Published by Cengage
ISBN 10: 1285740629
ISBN 13: 978-1-28574-062-1

Chapter 15 - Multiple Integrals - 15.4 Applications of Double Integrals - 15.4 Exercises - Page 1065: 9

Answer

$m$ = $\frac{1}{8}(1-3e^{-2})$ $(\frac{1-5e^{-2}}{1-3e^{-2}},\frac{8(1-4e^{-3})}{27(1-3e^{-2})})$

Work Step by Step

$m$ = $\int_0^1\int_0^{e^{-x}}xydydx$ $m$ = $\int_0^1[\frac{xy^2}{2}]_0^{e^{-x}}dx$ $m$ = $\frac{1}{2}\int_0^1xe^{-2x}dx$ $m$ = $\frac{1}{2}[-\frac{xe^{-2x}}{2}-\frac{e^{-2x}}{4}]_0^1$ $m$ = $\frac{1}{8}(1-3e^{-2})$ $x̄$ = $\frac{1}{m}\int_0^1\int_0^{e^{-x}}x^2ydydx$ $x̄$ = $\frac{8}{1-3e^{-2}}\int_0^1\int_0^{e^{-x}}x^2ydydx$ $x̄$ = $\frac{4}{1-3e^{-2}}\int_0^1[x^2y^2]_0^{e^{-x}}dx$ $x̄$ = $\frac{4}{1-3e^{-2}}\int_0^1x^2e^{-2x}dx$ $x̄$ = $\frac{4}{1-3e^{-2}}[-\frac{x^2e^{-2x}}{2}-\frac{xe^{-2x}}{2}-\frac{e^{-2x}}{4}]_0^1$ $x̄$ = $\frac{1-5e^{-2}}{1-3e^{-2}}$ $ȳ$ = $\frac{1}{m}\int_0^1\int_0^{e^{-x}}xy^2dydx$ $ȳ$ = $\frac{8}{1-3e^{-2}}\int_0^1\int_0^{e^{-x}}xy^2dydx$ $ȳ$ = $\frac{8}{3(1-3e^{-2})}\int_0^1[xy^3]_0^{e^{-x}}dx$ $ȳ$ = $\frac{8}{3(1-3e^{-2})}\int_0^1xe^{-3x}dx$ $ȳ$ = $\frac{8}{3(1-3e^{-2})}[-\frac{xe^{-3x}}{3}-\frac{e^{-3x}}{9}]_0^1$ $ȳ$ = $\frac{8(1-4e^{-3})}{27(1-3e^{-2})}$
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