Use logarithmic differentiation to find the derivative of the function:
y=(5x-4)^4 (x^5-6)^7 (7x^8+9)^9

Question

Use logarithmic differentiation to find the derivative of the function: 
y=(5x-4)^4 (x^5-6)^7 (7x^8+9)^9

anonymous · Answer

ln y=4ln(5x-4) etc

anonymous · Answer

like chguanas said.  take the log.  simplify using properties of the log.  then take the derivative of that, then multiply by the original mess.
$$4ln(5x-4)+7ln(x^5-6) +9ln(7x^8+9)$$

anonymous · Answer

derivative is 
$$\frac{20}{5x-4}+\frac{35x^4}{x^5-6}+\frac{504x^7}{7x^8+9}$$

anonymous · Answer

so something like this: 4 * (1/(5x-4)) * 5/1

anonymous · Answer

then just write that times the origial thing and you are done.

anonymous · Answer

ok got it thanks you so much

anonymous · Answer

yeah chain rule.
derivative of $$ln(f(x))=\frac{f'(x)}{f(x)}$$

anonymous · Answer

I have a final tomorrow and was really scare for that one