# \(\frac{d}{dx}\) and \(\frac{d^2}{dx^2}\)

**Calculus**Level 2

If \(\displaystyle\frac{d}{dx} f(x) = g(x)\) and \(\displaystyle\frac{d}{dx}g(x) = f(x^2)\), then \(\displaystyle\frac{d^2}{dx^2}f(x^3) =\ ?\)

\[ \begin{align} (A) &\quad f\left(x^6\right) & (B)&\quad g\left(x^3\right)\\ (C) &\quad 3x^2 g\left(x^3\right) & (D) &\quad 9x^4 f\left(x^6\right)+6x g\left(x^3\right)\\ (E) &\quad f\left(x^6\right) + g\left(x^3\right) & & \end{align} \]

*Credit: 1969 AP Calculus AB Exam*