Volume by double integral

We just started learning about nested integrals and this problem is way beyond me!!!!

I need to determine the volume under the f(x,y) = x^2 + y^2 and above the triangle where

y < or equal to x and x is > or equal to 0 but less than or equal to 9

I realize the first function is a circle and that the bounds for x are 0 and 9. I assume my function to integrate would be ( x^2 + y^2 - 1/2xy) dy dx but ........

Thanks to all of you helpful folks. I feel bad that I am not able to render math help of this caliber. I am providing free English tutoring at our junior college in an effort to continue the good work that I have found on this forum. Frostking