Question
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QUESIION 9
For certain function f , the first derivative is given as
9.1 Calculate the -coordinates of the stationary points of
9.2 For which values of is concave up
9.3 Determine the values of for which is strictly increasing?
9.4 If it is further given that and , determine the equation ol

Ask by Bartlett Salinas. in South Africa
Feb 11,2025

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Answer

9.1 The stationary points are at x = –3 and x = 1/3.
9.2 The function f is concave up for all x > –4/3.
9.3 f is strictly increasing when x < –3 or x > 1/3.
9.4 The equation of f is f(x) = x³ + 4x² – 3x – 18.

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Mind Expander

To find the -coordinates of the stationary points of , you need to set . This gives us the equation:
Using the quadratic formula , where , we can solve for :
This gives us two potential stationary points:
Now, let’s determine where is concave up by analyzing the second derivative, . Setting this greater than zero:
This means is concave up for .
Next, to find where is strictly increasing, we consider :
Looking at the roots we found earlier, the intervals for testing would be , , and . Testing points in each interval:
  • For (in ):
  • For (in ):
  • For (in ):
So, is strictly increasing in the intervals and .
Now, for the polynomial and knowing that , we can determine that .
We know is found by differentiating :
Setting this equal to the given first derivative yields:
Putting it all together:
With that, the complete polynomial function is determined!

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