How do you find the derivative of f(x) = log_x 2f(x)=logx2?

1 Answer
Apr 24, 2016

Change the base: log_x 2 = (ln2)/(lnx)logx2=ln2lnx

Explanation:

f(x) = log_x 2 = (ln2)/(lnx)f(x)=logx2=ln2lnx

I think maybe the quotient rule is clearest rather than rewriting any more.

f'(x) = ((0)(lnx)-(ln2)(1/x))/(lnx)^2

= -ln2/(x(lnx)^2)

If wished, we can rewrite again:

= -(ln2)/lnx 1/(xlnx)

= -log_x 2/(xlnx)