I don't have the time right now to answer, but a centroid problem [where I have worked out double integrals] was asked here...
--Chris
Find the centroid of the region bounded by
y=3x^2+6x, y=0 and x=3.
So what I've done so far
0<x<3
0<y<3x^2+6x
those are the bounds
and i take the double integral using those bound to find m
but I don't know what function to use I originally used 3x^2+6x but thats not correct.