# derivative of log function

• Apr 25th 2010, 08:58 PM
JGaraffa
derivative of log function
just want to make sure i'm doing this problem right, any help is appreciated.

find derivative:

log7x^2-1

= log7 + logx^2-1

= lnx^2-1 / ln7

=ln(x+1)(x-1) / ln7

= 1/ln7 + (1/x+1 * 1/x-1)

??
• Apr 25th 2010, 09:03 PM
Prove It
Quote:

Originally Posted by JGaraffa
just want to make sure i'm doing this problem right, any help is appreciated.

find derivative:

log7x^2-1

= log7 + logx^2-1

= lnx^2-1 / ln7

=ln(x+1)(x-1) / ln7

= 1/ln7 + (1/x+1 * 1/x-1)

??

Please use brackets where they're needed, this is too hard to read.

Is the function

$y = \ln{(7x^2)} - 1$?
• Apr 25th 2010, 09:04 PM
superman123
Here is the way to find the derivative of log functions;

$\frac{Derivative~of ~inside~of~ log}{inside~ of~ log}$

Is you function $\log(7x^2-1)$?

If yes, from the above rule $\frac{Derivative~of ~7x^2-1}{7x^2-1}=\frac{14x}{7x^2-1}$
• Apr 27th 2010, 06:30 PM
JGaraffa
ah i knew i forgot brackets somewhere.

the original problem was

log7(x^2-1)