AP Calculus AB / Unit 5: Analytical Applications of Differentiation
5.4 Using the First Derivative Test to Determine Relative (Local) Extrema
Notes
At a critical point $c$:
- $f'$ changes from $+$ to $-$: local max.
- $f'$ changes from $-$ to $+$: local min.
- No sign change: neither.
Practice
$f'(x)=x^2(x-2)$. At $x=0$, $f$ has:
$f'$ is negative on both sides of 0.
Using the same $f'$, at $x=2$, $f$ has:
$f'$ goes from negative to positive.
$f'$ changes from positive to negative at $x=4$. Then:
Increasing then decreasing.
Ready for more? Take the Unit 5 test.