Derivative help

**^_^Engineer_Adam^_^** · December 1st 2006, 09:10 PM

$D_r (\frac{2r+3}{3r-2})$

**CaptainBlack** · December 2nd 2006, 12:18 AM

Originally Posted by ^_^Engineer_Adam^_^

$D_r (\frac{2r+3}{3r-2})$

You need the quotient rule:

$D_r \frac{f(r)}{g(r)}=\frac{g(r)f'(r)-f'(r)g(r)}{[g(r)]^2}$

here:

$f(r)=2r+3$ ,

$f'(r)=2$ ,

$g(r)=3r-2$ ,

$g'(r)=3$

so:

$D_r \left( \frac{2r+3}{3r-2} \right)=\frac{g(r)f'(r)-f(r)g'(r)}{[g(r)]^2}<br /> =\frac{2(3r-2)-3(2r+3)}{(3r-2)^2}=-\frac{13}{(3r-2)^2}<br />$

RonL

**ThePerfectHacker** · December 2nd 2006, 01:37 PM

Originally Posted by CaptainBlank

so:

$D_r \left( \frac{2r+3}{3r-2} \right)=\frac{g(r)f'(r)-f(r)g'(r)}{[g(r)]^2}<br /> =\frac{2(3r-2)-3(2r+3)}{(3r-2)^2}=-\frac{13}{(3r-2)^2}<br />$

I see you learned the quotient rule!

**CaptainBlack** · December 2nd 2006, 01:42 PM

Originally Posted by ThePerfectHacker

I see you learned the quotient rule!

I'm afraid not; I derived it.

RonL

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