a) N1(5/0) N2(-13/0) A(0/-520) in Scheitelpunktform.
f(x) = a * (x - 5) * (x + 13)
f(0) = a * (0 - 5) * (0 + 13) = -520 --> a = 8
f(x) = 8 * (x - 5) * (x + 13)
Sx = (5 - 13) / 2 = -4
Sy = f(-4) = 8 * (-4 - 5) * (-4 + 13) = -648
f(x) = 8 * (x + 4)^2 - 648
