You can't possibly have even set up the double integral properly - if you are integrating with respect to first then your innermost bounds need a function of , not .
Please post the entire question.
ummm no Prove it is correct. You have written
Do you See the problem with what you posted. You are integrating with respect to y first and have it as a function of y. That does not make sense. After integration you would still have y's in your integrand but no y differential.