a)
f(0) = 0
f''(0) = 0
f(3) = 0
f(5) = 5
d = 0
2b = 0
27a + 9b + 3c + d = 0
125a + 25b + 5c + d = 5
f(x) = 0,0625·x^3 - 0,5625·x
b)
f(0) = 0
f''(0) = 0
f(6) = 5.5
f(3) = 0.5
d = 0
2b = 0
216a + 36b + 6c + d = 5,5
27a + 9b + 3c + d = 0,5
f(x) = 1/36·x^3 - 1/12·x