Derivative of logarithmic function

Question

If the function $f(x)=\log_{2x}x^2$ is given, what is $f'(4)$?

I tried to use the formula for derivative of logarithm but here the base is $2x$, so it made me confused.

Note that the answer is $1/(18\ln 2)$.

Are you expecting that people will fix your questions all the time? — Kaster, Aug 21 '13 at 23:45
@Kaster Sorry if I made a mistake but what do you mean by fixing? — guest, Aug 21 '13 at 23:47
@guest I meant your inability to learn how to format math after asking 4 questions. — Kaster, Aug 21 '13 at 23:48
@guest - I've fixed up the question, please look at the formatting so you can learn how to do it yourself next time. — Nathaniel Bubis, Aug 21 '13 at 23:49

score 4 · Accepted Answer · answered Aug 21 '13 at 23:46

4

Hint:

Note that: $$\log_b a = \frac{\ln a}{\ln b}$$ Now you can use the formula for the derivative of a fraction.

answered Aug 21 '13 at 23:46

Nathaniel Bubis

1 Answers1