Solving CALC AB Problems for f'(2)=3

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Homework Help Overview

The discussion revolves around finding the value of a constant \( k \) in the function \( f(x) = \ln(3x + 2)^k \) given that the derivative at \( x = 2 \) equals 3. Participants are exploring the implications of this condition on the derivative and the value of \( k \).

Discussion Character

  • Exploratory, Assumption checking, Mathematical reasoning

Approaches and Questions Raised

  • Participants discuss the correctness of the derivative calculation and question the validity of the proposed answer of \( k = 8 \). There is an exploration of how to find \( k \) without a calculator, and one participant suggests using logarithmic properties to assist in the reasoning.

Discussion Status

The discussion is ongoing, with some participants expressing doubt about the correctness of the answer provided in the textbook. There is a recognition of the need to clarify the derivative's implications and the value of \( k \), but no consensus has been reached.

Contextual Notes

Participants note that the problem constraints include a prohibition on calculator use, which may affect their approach to solving for \( k \).

coookiemonste
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Homework Statement


Let f be the functions f(x)=ln(3x+2)^k for some positibe constant k.
If f'(2)=3, what is the value of k?
the answer is 8,but i don't think i am taking the derivative right.



Homework Equations


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The Attempt at a Solution


f'(x)=3k*ln(3x+2)^(k-1)/(3x+2)
then i plugged in (2,3) into the derivative above.
and i got k=8/(ln8)(8^(k-1))
 
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The derivative is correct, but the answer is not 8. If you plug in (2,3) into your derivative with k=8, you will get a contradiction.
 
my ap book says the answer is 8, however it may be wrong.
but how would you find the value of k?
i am not allowed to use a calculator with this problem.
 
try using the fact that

[tex]log_a b^r=rlog_a b[/tex]
 
AH!
thank you!
 

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