Answer: x ≥ 6
Step-by-step explanation:
Since
(density = mass/volume), we can get the mass/weight of the liquid by integrating the density
over the interior of the tank. This is done with the integral

which is more readily computed in cylindrical coordinates as

The square root of 72 is rational because the answer can be a real number.
No solution for the quadratic equation because of the √-20