# The Marginal pdf of a Function

## Homework Statement

The integral from 0 to infinity of xe^[-x(1+y)]dy

## 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.

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

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

Yes! You're right! Something was bugging me about that big fat zero. I knew I needed another set of eyes. Thanks a lot!