Mark M. answered 01/15/19
Retired math prof. Calc 1, 2 and AP Calculus tutoring experience.
I think that you mean: f"(x) = 36x, f'(0) =3, and f(0) = 2
Since f"(x) = 36x, f'(x) = ∫36xdx = 18x2 + C1
f'(0) = 3, so 0 + C1 = 3, C1 = 3
f'(x) = 18x2 + 3
f(x) = ∫f'(x)dx = ∫(18x2 + 3)dx
f(x) = 6x3 + 3x + C2
f(0) = 2, so 0 + 0 + C2 = 2, C2 = 0
f(x) = 6x3 + 3x + 2