f(x) = 2/x
m = (f(4 + h) - f(4)) / h
m = (2/(4 + h) - 0.5) / h
m = (2/(4 + h) - 0.5(4 + h)/(4 + h)) / h
m = (2 - 0.5(4 + h)) / (4 + h) / h
m = (2 - 2 - 0.5h) / (4 + h) / h
m = (-0.5h) / (4 + h) / h
m = -0.5 / (4 + h)
Grenzwert für h gegen 0
m = -0.5 / (4 + 0) = -0.5/4 = -1/8