Solution. Let F(x) = e^{x^3}, f(u) = e^{u} and g(x) = x^3 such that F(x) = f(g(x)). We will use the chain rule:
\begin{align*} F'(x) = f'(g(x))g'(x). \end{align*}
\begin{align*} f'(g(x)) = e^{g(x)} = e^{x^3} \quad \text{and} \quad g'(x) = 3x^2. \end{align*}
\begin{align*} F'(x) &= f'(g(x))g'(x) \\ &= e^{x^3} \cdot 3x^2 \\ &= 3e^{x^3} x^2. \end{align*}