What is x^3 4x^2=225?

First off you need to take the square root of both sides and it leaves you with (x) (2x) = 15 then you multiple the x and it gives you 2x^2=15 then you divide by 2 and it gives you 7.5 then you take the square root of that to cancel the x^2 and it gives you x=2.7