This problem is incorrect in itself. x^3+4x^2=150.
So x^3+4x^3 cannot=150
Meant to say "A cuboid has a square base of side x cm. The height of the cuboid is (x + 4) cm. The volume of the cuboid is 150cm cubed. Show that x cubed + 4 squared = 150?"
4 x squared = 150?
ok, so since volume of a cuboid is (base length)^2 * height, you set up the volume as x^2*(x+4)=150. then, you distribute the x^2 and you get x^3+4x^2=150.