Important formulas
d (ab )/ dx = 0 This is a constant
d ( xn ) / dx = nxn -1 Power Rule
d (a x ) / dx = a x ln a Derivative of an exponential function
d ( x x )/dx = x x (1 + ln x ) Logarithmic Differentiation
It is sometimes easy to get these several functions confused & use the wrong rule for differentiation. Always remember that each rule has extremely particular rules for where the variable & constants must be. For instance, the Power Rule needs that the base be a variable and the exponent are a constant, whereas the exponential function needs accurately the opposite.
If you can keep straight all of the rules you can't go wrong along with these.