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differential of ln(1+x)-1

 Nov 22, 2016
 #1
avatar+118653 
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differential of ln(1+x)-1

 

 

\(\boxed{\frac{d}{dx}lnf(x)=\frac{f'(x)}{f(x)}}\)

 

 

\(\frac{d}{dx}\;[ln(1+x)^{-1}]\\ =\frac{d}{dx}\;[-ln(1+x)]\\ =\frac{-1}{1+x}\\\)

 Nov 22, 2016
 #2
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Take ln(1+x) as t.

Find dt in terms of dx.

Replace dx with (1+x)dt.

Solve for d/dt of transformed expression.

The answer is: -[ln(1+x)]-2 / (1+x)

 Nov 22, 2016
 #3
avatar+118653 
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Only the (1+x) is raised to the -1

 

IT IS NOT      (ln(1+x))^-1

Melody  Nov 22, 2016
 #4
avatar+33653 
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The difference between Melody's and DarkStrider's answer is:

 

Melody has interpreted the expression as  ln[(1+x)^-1]

 

DarkStrider has interpreted it as    [ln(1+x)]^-1

 

Different expressions give different results!

 Nov 22, 2016

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