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October 3rd, 2014, 08:08 PM   #1
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Question Derivative without using properties of logarithms

y = ln[(2x+8 ) / ( 8x+25)]

After deriving, I come to

$\displaystyle \frac{1}{\dfrac{2x+8}{8x+25}}\left(-\frac{14}{(8x+25)^2}\right)$

Could someone fully show me how to simplify this further?

EDIT: I get to negative 7/(x+4)(8x+25)^3 but wolfram says that ^3 is not supposed to be there for (8x+25)....

Last edited by MarkFL; October 3rd, 2014 at 10:47 PM. Reason: Restore gutted content
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October 3rd, 2014, 10:45 PM   #2
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What you want is:

$\displaystyle \frac{1}{\dfrac{2x+8}{8x+25}}\left(-\frac{14}{(8x+25)^2}\right)=-\frac{2\cdot7(8x+25)}{2(x+4)(8x+25)^2}=-\frac{7}{(x+4)(8x+25)}$

By the way, please do not edit a post once you have solved the question to remove the original question. Gutting a thread this way leaves behind a useless post.
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