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The Marginal pdf of a Function

  1. Mar 17, 2010 #1
    1. The problem statement, all variables and given/known data The integral from 0 to infinity of xe^[-x(1+y)]dy

    2. Relevant equations

    3. The attempt at a solution

    I can't figure out why the answer would be zero to a pdf. Also, for the indefinite integral the calculator produces the answer xy*e^(-x-xy). I cant' figure out how to get that answer, nor can I figure out if it would even matter if I was able to.

    I guess I'm just asking for another set of eyes to look over my work and see if there is something that I am missing.
  2. jcsd
  3. Mar 17, 2010 #2
    aren't you supposed to get -e^(-x)

    when you plug 'b' into y, the term becomes zero.
    but when you plug zero, it becomes -e^(-x)*1
  4. Mar 17, 2010 #3
    Yes! You're right! Something was bugging me about that big fat zero. I knew I needed another set of eyes. Thanks a lot!
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