Well, find , , , ... and see when it becomes 0. Of course, you need to know what the definition of is.
On my latest assignment in high school calculus to do over the Spring Break, I've been given this problem: "What is the smallest n for which d^n(12x^3 + 2x) / dx^n = 0, for all x?" - I don't know where to start with this, but my teacher mentioned something about finding the derivatives. Can someone here please help point me in the right direction?