Remember that the derivative of a sum (or difference) is just the sum (or difference) of the derivatives, and that the derivative of a constant multiple is the constant times the derivative of the remaining factor.

Also, you really must be familiar with the basic differentiation rules. Be sure to study them. For this problem, you need to know

and

(where is a constant).

Good luck! If you still have trouble, be more specific about where your difficulties lie.