The formula is
.. V = (4/3)π*abc
where a, b, c are the semi-axes of the ellipsoid.
The semi-axes are the values of x, y, z that satisfy the equation when the other terms are zero. Here, they are a=9, b=9, c=3, so the volume is
.. V = (4/3)π*9*9*3 = 324π . . . . cubic units
.. V ≈ 1017.9 units³
