Advanced calculus

[Hira Javaid]

Need help please. I need the hints of how to solve this please.
A parametrized surface S is given by G(u,v)=(u-v, u+v, uv) where u²+v²≤1 evaluate the average value of the function f(x,y,z)=x²+y² over S

 

[blamocur]

To start, you need to express [imath]f[/imath] as a function of [imath]u,v[/imath], then express the surface area differential on [imath]S[/imath] in terms of [imath]du,dv[/imath].