f(x) = (x2 - 4) / (x - 3)2
f'(x) = ((2·x)·(x - 3)2 - (x2 - 4)·2·(x - 3)) / (x - 3)4
f'(x) = ((2·x)·(x - 3) - (x2 - 4)·2) / (x - 3)3
f'(x) = (2·x2 - 6·x - 2·x2 + 8) / (x - 3)3
f'(x) = (8 - 6·x) / (x - 3)3
f''(x) = (- 6·(x - 3)3 - (8 - 6·x)·3·(x - 3)2) / (x - 3)6
f''(x) = (- 6·(x - 3) - (8 - 6·x)·3) / (x - 3)4
f''(x) = (18 - 6·x + 18·x - 24) / (x - 3)4
f''(x) = (12·x - 6) / (x - 3)4