原式=∫√ydy∫xdx
=(1/2)∫√y(y-y^4)dy
=(1/2)∫[y^(3/2)-y^(9/2)]dy
=(1/2)[(2/5)y^(5/2)-(2/11)y^(11/2)]│
=(1/2)(2/5-2/11)
=6/55