Aufgabe 2
Author: G. Kremb

a = 4 (slider from -5 to 5, step 0.1)
f_a(x) = -(x - a) (x + 2)^(2) / 8
t_a(x) = 1 / 2 * (a - 1) x + a / 2
EXTREMUM: (2 / 3 a - 2 / 3, f_a(2 / 3 a - 2 / 3))
B = (-1, 0.5)