f ( 2 ) = a*24 + b*23 + c*22 + 12*2 = 0
f ´ ( 2 ) ) = 4*a*23 + 3*b*22 + 2*c*2 + 12 = 0
f ´´ ( 2 ) = 12 * a * 22 + 6 * b * 2 + 2 * c = 0
16a + 8b + 4c + 24 = 0
32a + 12b + 4c + 12 = 0
48a + 12b + 2c = 0
16a + 8b + 4c + 24 = 0
32a + 12b + 4c + 12 = 0 | abziehen
--------------------------------
-16a - 4b + 12 = 0
48a + 12b + 2c = 0 | * 2
96a + 24b + 4c = 0
32a + 12b + 4c + 12 = 0
96a + 24b + 4c = 0 | abziehen
-------------------------
-64a - 12b +12 = 0
-16a - 4b + 12 = 0 | * 3
-64a - 12b = 0
-48a - 12b + 36 = 0
-64a - 12b +12 = 0 | abziehen
-------------------
16a + 24 = 0
a = -3/2