Answer:
a) The critical points are
and
.
b) f is decreasing in the interval ![(-\infty, -6)](https://tex.z-dn.net/?f=%28-%5Cinfty%2C%20-6%29)
f is increasing in the intervals
and
.
c) Local minima: ![x = -6](https://tex.z-dn.net/?f=x%20%3D%20-6)
Local maxima: No local maxima
Step-by-step explanation:
(a) what are the critical points of f?
The critical points of f are those in which
. So
![f^{\prime}(x) = 0](https://tex.z-dn.net/?f=f%5E%7B%5Cprime%7D%28x%29%20%3D%200)
![(x-3)^{2}(x+6) = 0](https://tex.z-dn.net/?f=%28x-3%29%5E%7B2%7D%28x%2B6%29%20%3D%200)
So, the critical points are
and
.
(b) on what intervals is f increasing or decreasing? (if there is no interval put no interval)
For any interval, if
is positive, f is increasing in the interval. If it is negative, f is decreasing in the interval.
Our critical points are
and
. So we have those following intervals:
![(-\infty, -6), (-6,3), (3, \infty)](https://tex.z-dn.net/?f=%28-%5Cinfty%2C%20-6%29%2C%20%28-6%2C3%29%2C%20%283%2C%20%5Cinfty%29)
We select a point x in each interval, and calculate
.
So
-------------------------
![(-\infty, -6)](https://tex.z-dn.net/?f=%28-%5Cinfty%2C%20-6%29)
![f^{\prime}(-7) = (-7-3)^{2}(-7+6) = (100)(-1) = -100](https://tex.z-dn.net/?f=f%5E%7B%5Cprime%7D%28-7%29%20%3D%20%28-7-3%29%5E%7B2%7D%28-7%2B6%29%20%3D%20%28100%29%28-1%29%20%3D%20-100)
f is decreasing in the interval ![(-\infty, -6)](https://tex.z-dn.net/?f=%28-%5Cinfty%2C%20-6%29)
---------------------------
![(-6,3)](https://tex.z-dn.net/?f=%28-6%2C3%29)
![f^{\prime}(2) = (2-3)^{2}(2+6) = (1)(8) = 8](https://tex.z-dn.net/?f=f%5E%7B%5Cprime%7D%282%29%20%3D%20%282-3%29%5E%7B2%7D%282%2B6%29%20%3D%20%281%29%288%29%20%3D%208)
f is increasing in the interval
.
------------------------------
![(3, \infty)](https://tex.z-dn.net/?f=%283%2C%20%5Cinfty%29)
![f^{\prime}(4) = (4-3)^{2}(4+6) = (1)(10) = 10](https://tex.z-dn.net/?f=f%5E%7B%5Cprime%7D%284%29%20%3D%20%284-3%29%5E%7B2%7D%284%2B6%29%20%3D%20%281%29%2810%29%20%3D%2010)
f is increasing in the interval
.
(c) At what points, if any, does f assume local maximum and minima values. ( if there is no local maxima put mo local maxima) if there is no local minima put no local minima
At a critical point x, if the function goes from decreasing to increasing, it is a local minima. And if the function goes from increasing to decreasing, it is a local maxima.
So, for each critical point is this problem:
At
, f goes from decreasing to increasing.
So
, f assume a local minima value
At
, f goes from increasing to increasing. So, there it is not a local maxima nor a local minima. So, there is no local maxima for this function.