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## Main Question or Discussion Point

f(x) = ln (12x-5/9x-2)

f'(x) = (4/3) (1/ln10)(9x-2/12x-5)

Is this correct??

f'(x) = (4/3) (1/ln10)(9x-2/12x-5)

Is this correct??

- Thread starter fr33pl4gu3
- Start date

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f(x) = ln (12x-5/9x-2)

f'(x) = (4/3) (1/ln10)(9x-2/12x-5)

Is this correct??

f'(x) = (4/3) (1/ln10)(9x-2/12x-5)

Is this correct??

CompuChip

Science Advisor

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Also, I think you didn't do the chain rule quite right.

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Then, is this

f(x) = ln (12x-5)

g(x) = ln (9x-2)

f'(x) = 12/12x-5

g'(x) = 9/9x-2

Correct??

f(x) = ln (12x-5)

g(x) = ln (9x-2)

f'(x) = 12/12x-5

g'(x) = 9/9x-2

Correct??

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Is this correct:

(12/12(ln9x-2)-5)-(9/9x-2)

(12/12(ln9x-2)-5)-(9/9x-2)

Last edited:

Defennder

Homework Helper

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This should not have ln inside. What is d/dx ln(12x-5) ? You've got it from above, just put it into this one.fr33pl4gu3 said:(12/12(ln9x-2)-5)-(9/9x-2)

CompuChip

Science Advisor

Homework Helper

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set y = (12x - 5) / (9x - 2). Then the derivative of ln(y) is 1/y . dy/dx.

The other way is to first use ln(a/b) = ln(a) - ln(b) and then use the sum rule to differentiate (you still need the chain rule!).

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