How Do You Calculate P(X>4Y) with the Given Joint PDF?

[Phox]

Homework Statement

Suppose X and Y have the joint probability density function:

f(x,y) = x+4y, 0<y<x<1
f(x,y) = 0 otherwise

Find P(X>4Y)

Homework Equations

The Attempt at a Solution

I'm not sure how to do this. I've already found marginal pdf's for x and y.. although I don't know if they're relevant.

p1(x) = 3x^2
p2(y) = (-9/2)y^2+4y+(1/2)

Thanks for the help

 

[BruceW]

I agree with your values for the marginals. Although I don't think they are relevant for this question.. There may be a way to do it, making use of the marginals, but that is not the way I did it.

You should start by writing an equation for P(X>4Y) using the equation f(x,y)