It's simple. If you have a formula when you study in Grade Three, you will know that it is very simple. This is called derivative: the derivative of x is 1, the derivative of X 2 is 2x, the derivative of X 3 is 3x 2, and the derivative of X N is NX N- 1. The derivative of a constant is 0 (for example, the derivative of 3 is 0). The derivative of the constant is 3x 2.