Anzuwenden ist die Produktregel
u = 1020 - 40t
u´= -40
v = e1/10*t = e0.1*t
v´ = e1/10*t * (1/10) = e0.1*t * 0.1
( u * v ) ´ = u´ * v + u * v´
f(t)=(1020 - 40t) x e1/10t
f ´( t ) = -40 * e0.1*t + ( 1020 - 40t ) * e0.1*t * 0.1
f ´( t ) = e0.1*t * ( -40 + 102 - 4t )
f ´( t ) = e0.1*t * ( 62 - 4t )