Let - this was chosen to make the denominator easier
When we differentiate u wrt x we get which is obtained through normal rules.
To be able to substitute our du term into the equation we need to isolate dx: . However that isn't very helpful so to get that e^x out the way rearrange the original substitution
(that was a mistake I made in my previous post. It should read the above)
Putting this back into the integral for dx: