This skill is located in Section 3.3. See First Derivative Test.
The First Derivative Test determines whether a critical point is a local maximum, local minimum, or neither:
At a critical point $c$ where $f'(c) = 0$ or $f'(c)$ doesn't exist:
| $f'$ changes from... | At $c$, $f$ has... |
|---|---|
| $+$ to $-$ | Local maximum |
| $-$ to $+$ | Local minimum |
| No sign change | Neither |