Approximative Schar von Tangenten bzw. Parablen
y =x³ - x, y' = 3x² - 1, y'' = 6x
y= ax+b: k³ - k = a k + b, 3k² - 1 = a => b = -2k³
Tangentenschar: y = (3k² - 1)x - 2k³, -3<k<3
y= cx²+dx+e: k³ - k = ck² + dk + e, 3k² - 1 = 2ck + d, 6k = 2c => c=3k => d=-1-3k², e=k³
Parabelschar: y =3kx² - (1+3k²)x + k³, -3<k<3