12 c)
f(x) = 2·x^2 - 3·x
(f(x + h) - f(x)) / h = ((2·(x + h)^2 - 3·(x + h)) - (2·x^2 - 3·x)) / h
(f(x + h) - f(x)) / h = ((2·(x^2 + 2·h·x + h^2) - 3·(x + h)) - (2·x^2 - 3·x)) / h
(f(x + h) - f(x)) / h = ((2·x^2 + 4·h·x + 2·h^2 - 3·x - 3·h) - (2·x^2 - 3·x)) / h
(f(x + h) - f(x)) / h = (2·x^2 + 4·h·x + 2·h^2 - 3·x - 3·h - 2·x^2 + 3·x) / h
(f(x + h) - f(x)) / h = (4·h·x + 2·h^2 - 3·h) / h
(f(x + h) - f(x)) / h = (4·x + 2·h - 3)
für lim (h --> 0)
f'(x) = 4·x - 3