Finding Critical Numbers for a Polynomial Function with Power and Chain Rules

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Homework Help Overview

The discussion revolves around finding the critical numbers of the polynomial function F(x) = x^{\frac{4}{5}}(x-4)^{2}. Participants are exploring the application of differentiation rules, specifically the power rule, chain rule, and product rule, in the context of this problem.

Discussion Character

  • Exploratory, Conceptual clarification, Mathematical reasoning

Approaches and Questions Raised

  • Participants discuss the differentiation of the function using various rules and express uncertainty about the correct application of these rules. There is mention of two known critical numbers, 0 and 4, while a third critical number remains elusive. Some participants suggest alternative forms of the function to aid in understanding.

Discussion Status

The discussion is ongoing, with participants providing insights into different methods of differentiation. Some guidance has been offered regarding the use of the product rule, and there is an acknowledgment that both methods should yield consistent results, although algebraic confirmation may be necessary.

Contextual Notes

Participants are navigating the complexities of applying multiple differentiation rules and are questioning the completeness of their approaches. There is an emphasis on ensuring that all critical numbers are identified, which may require further exploration of the function's behavior.

frosty8688
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1. Find the critical numbers of [itex]F(x) = x^{\frac{4}{5}}(x-4)^{2}[/itex]



2. Power rule then chain rule



3. [itex]F'(x) = \frac{4}{5}x^{\frac{-1}{5}} (x-4)^{2}*2(x-4)[/itex] I know two critical numbers are 0 and 4 and I am having problems finding the third one.
 
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frosty8688 said:
1. Find the critical numbers of [itex]F(x) = x^{\frac{4}{5}}(x-4)^{2}[/itex]
2. Power rule then chain rule
and product rule?
frosty8688 said:
3. [itex]F'(x) = \frac{4}{5}x^{\frac{-1}{5}} (x-4)^{2}*2(x-4)[/itex]
The first rule to use would be the product rule. It doesn't look to me like you used that rule.
frosty8688 said:
I know two critical numbers are 0 and 4 and I am having problems finding the third one.
 
Another way to do this is to write
[tex]F(x)= x^{\frac{4}{5}}(x^2- 8x+ 16)= x^{\frac{14}{5}}- 8x^{\frac{9}{5}}+ 16x^{\frac{4}{5}}[/tex]
 
That makes it easier to understand.
 
Yes, but it would also be useful to use the product rule (correctly). The results should be the same for either method, but you might need to use some algebra to confirm that they are the same.
 

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