When a power is taken on both sides of an equation, the resulting solutions might not check in the original radical equation. These are called extraneous solutions. You must check solutions by substituting in the values into the original equation and verifying that it produces a true statement.
Volume of a cylinder is pi*(radius)^2* height. pi is 3.14 and radius is half of diameter which would be 3. height is 8. Thus volume of a cylinder in your case is pi*9*8 or 72*pi which is approximately 226.19