The Joint Probability Density Function of X and Y is

f(x,y) = c(y^2 - 64x^2)e^-y, -y/8<= x <= y/8, 0<y<infinity

So the integral would look something like this?

$\displaystyle \int_{0}^{\inf} \int_{-y/8}^{y/8} (y^2-64x^2)e^{-y} dxdy $

Find c and the expected Value of X.

But I don't know how where to go from here or how to get the expected value

C is supposed to be 1 and E[X] should be 0.