hvordan differentierer jeg dette stykke? hjæælp

Brug reglerne:

f(x) = g(x) + h(x) ⇔ f '(x) = g'(x) + h'(x)

f(x) = a xⁿ ⇔ f '(x) = a n x^n-1

            A(h)      =   (20 - 2*h)*h

                         =    20h  -  2h²

            A'(h)     =    20    -  4h                                      A(h) = a*hⁿ        ⇔       A'(h) = n*a*h^n-1

                                                                         Fx:     A(h) = 3h⁴           ⇔       A'(h) = 3*4*h^4-1

                                                   Hvor 3=a , n=4                                    ⇔      A'(h) = 12h³