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thomas49th
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Homework Statement
Let [tex]I_{n} = \int^{2}_{0} x^{n}e^{x} dx[/tex] where n is a positive integer. Use integration by parts to show
that
[tex]
2^{n}e^{2} - nI_{n-1}
[/tex]
By first finding
[tex]I_{1} = \int ^{2}_{0} xe^{x} dx [/tex]
find I2 and I3.
Homework Equations
I'm sure your all aware of the formula for Int by parts. We'll take the [tex]e^{x}[/tex] function as the one to integrate and the [tex]x^{n}[/tex] as the one to differentiate.
The Attempt at a Solution
So use integration by parts to find In:[tex]x^{n}e^{x} - n\int^{2}_{0}x^{n-1}[/tex]
Well that's
[tex]x^{n}e^{x} - nI_{n-1}[/tex]
is it not?
So now put the limits in
[tex][x^{n}e^{x} - nI_{n-1}]^{2}_{0}[/tex]
[tex][2^{n}e^{2} - nI_{n-1}] - [ - nI_{n-1}][/tex]
but that's isn't right because I'm getting no [tex] nI_{n-1}[/tex] because they cancel!
Where have I gone wrong?
Thanks
Thomas
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