## Calculus (3rd Edition)

$F(x)$ is the antiderivative of $f(x)$.
Since $$F(x)'= \frac{1}{3}((x+13)^3)'=\frac{3}{3}(x+13)^2=((x+13)^2=f(x)$$ thus $F(x)$ is the antiderivative of $f(x)$.