Critical points is where the derivative (slope) is zero or does not exist. So to do this we have to find the derivative of our function:

So we apply chain rule:
=

Set our first derivative to zero and solve for x:
3(x^2 - 1) * 2x = 0
So we can see that (by plugging in) 0, -1 and 1 makes our solution true
So our critical value is x = 0, x = -1, x = 1
Answer:
90°
Step-by-step explanation:
Given - Mariyam wants to cut her chocolate brownie into two rectangles.
To find - What kind of angles will Mariyam form?
Proof -
If she cut the brownie in the rectangular shape, then the angle formed is 90°.
It will be b because you will have to time $3.50P140= 490