Chapter 4 - Applications of the Derivative - 4.2 What Derivatives Tell Us - 4.2 Exercises - Page 259: 99

There are no critical points and hence no local extremas.

$f'(x) = 3x^2 + 4x + 4$, which is never $0$. (Note that the discriminant $42 − (4)(3)(4) < 0$, so this quadratic has no real roots.) So there are no critical points.