Derivative of f(x)=ln(e^6x^2-4x+5)-e^ln(7x-8)+12e

nell

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Nov 17, 2008
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Hello,
I am in need of assistance on the problem below. I am not sure how to go about solving this equation. Your knowledge and assistance will be appreciated.

f(x)=ln(e^6x^2-4x+5)-e^ln(7x-8)+12e
 
nell said:
Hello,
I am in need of assistance on the problem below. I am not sure how to go about solving this equation. Your knowledge and assistance will be appreciated.

f(x)=ln(e^6x^2-4x+5)-e^ln(7x-8)+12e

Just differentiate term by term - using chain rule - i.e.

\(\displaystyle \frac{d}{dx}[f[g(x)] \, = \, \frac {df}{dg} \cdot \frac{dg}{dx}\)

also use

\(\displaystyle e^{ln(a)} \, = \, a\)

and

\(\displaystyle ln[e^a] \, = \, a\)

Please show us your work, indicating exactly where you are stuck, so that we know where to begin to help you.
 
Hello,
I have noted below what I came up with. I thank you in advance for your assistance.
f'(x)=(6e^6x^2-4)-e^7+12e
 
nell said:
Hello,
I have noted below what I came up with. I thank you in advance for your assistance.
f'(x)=(6e^6x^2-4)-e^7+12e <<< This is incorrect. Please show us detailed work

Specially, 12e is constant - when you differentiate a constant you get 0.

Follow the hints I provided you - show us steps through those hints.
 
I am confused. My professor has the class using the generalized power rule rather than the chain rule. So, I am unfamiliar with working out the problem as you suggested. I tried it again, and I came up with the following:
f'(x)=12x-4+7-8
f'(x)=12x-5

As always, your assistance is appreciated.

Thanks
 
nell said:
e^6x^2-4x+5 ? I cannot determine what this expression is supposed to mean.

Please point to Forum Help at the top of this page and click on "Karl's Notes -- Typing Math" to learn how to post expressions unambiguously.

 
sorry about that. I have corrected it.
f(x)=ln(e^6x2-4x+5)-e^ln(7x-8)+12e
 
nell said:
sorry about that. I have corrected it.
f(x)=ln(e^6x2-4x+5)-e^ln(7x-8)+12e

Does your problem look like:


\(\displaystyle f(x) \, = \, ln[e^{6x^2 \, - 4x \, +5}] \, - \, e^{ln(7x-8)} \, + \, 12e\)

This should be written as (in ASCII format):

f(x)=ln(e^(6x^2-4x+5))-e^ln(7x-8)+12e


or does it look like:

\(\displaystyle f(x) \, = \, ln[e^{6x^2} \, - 4x \, +5] \, - \, e^{ln(7x-8)} \, + \, 12e\)
{this is the way wrote it}
 
The first one is correct. sorry about that.
This should be written as (in ASCII format):

f(x)=ln(e^(6x^2-4x+5))-e^ln(7x-8)+12e
 
Then use the hints I gave you to simplify the expression first

\(\displaystyle e^{ln(a)} \, = \, a\)

and

\(\displaystyle ln(e^a) \, = \, a\)

- then take derivative.
 
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