f(x) = x^3 - x
m = (f(x + h) - f(x)) / h
m = (((x + h)^3 - (x + h)) - (x^3 - x)) / h
m = ((x^3 + 3·h·x^2 + 3·h^2·x + h^3 - x - h) - (x^3 - x)) / h
m = (x^3 + 3·h·x^2 + 3·h^2·x + h^3 - x - h - x^3 + x) / h
m = (3·h·x^2 + 3·h^2·x + h^3 - h) / h
m = 3·x^2 + 3·h·x + h^2 - 1
Für lim h → 0
m = 3·x^2 - 1