- #1
Kaldanis
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Homework Statement
[itex] \int_{1}^{2} x^2 e^{x} dx [/itex]
Homework Equations
Integrating by parts. Writing out chain rule, integrating both sides and rearranging gives ∫f(x)g'(x) dx = f(x)g(x) - ∫f'(x)g(x) dx
The Attempt at a Solution
[itex] \int_{1}^{2} x^2 e^{x} dx = \left[x^2 e^x\right]_{1}^{2} - \int_{1}^{2} 2x e^{x} dx[/itex]
Applying again gives:
[itex] \int_{1}^{2} x^2 e^{x} dx = \left[x^2 e^x\right]_{1}^{2} - \left(\left[2x e^x\right]_{1}^{2} - \int_{1}^{2} 2 e^{x} dx\right)[/itex]
Integrating last term gives:
[itex] \int_{1}^{2} x^2 e^{x} dx = \left[x^2 e^x\right]_{1}^{2} - \left(\left[2x e^x\right]_{1}^{2} - \left[2e^x\right]_{1}^{2}\right)[/itex]
When I simplify this I get -2e2 + 3e, however I know the answer should be 2e2-e.
Can someone please point out where my mistake is?