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.