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Help with integration

  • Thread starter confused88
  • Start date
  • #1
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Homework Statement


Can someone please help me with integration of x(e^(-x-theta)) Thank you. My working is shown below

The Attempt at a Solution


u = x, du = 1 dx, dv = e^(-x-theta)) v = e^-x+theta+1 / theta + 1

the rest can be seen in the attachment. Can you please check it out, it would be greatly appreciated.Thanks
 

Attachments

Answers and Replies

  • #2
726
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The attachment is pending approval so I can't see it.

Use the substitution [tex] u = -x - \theta \Rightarrow x = -(u+\theta) \Rightarrow dx = -du [/tex]. So our integral is now [tex] \int (u + theta)e^u du [/tex].

Now use integration by parts.
 
  • #3
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ohhh wow thanks a lot!!
 
  • #4
HallsofIvy
Science Advisor
Homework Helper
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The first thing I would do is write [itex]e^{-x- \theta}= e^{-x}e^{-\theta}[/itex] and factor out the [itex]e^{-\theta}[/itex]. Your integral is just [itex]e^{-\theta}\int xe^{-x}dx[/itex] which can be done by integration by parts.
 

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