How do you find the derivative of 5ln(7x+6ln(x))5ln(7x+6ln(x))?

1 Answer
May 25, 2015

SImple: you use the chain rule!

The chain rule states that

(dy)/(dx)=(dy)/(du)(du)/(dx)dydx=dydududx

Thus, we just need to rename u=7x+6ln(x)u=7x+6ln(x) (consequently our original function becomes 5ln(u)5ln(u)), and now derivate it all part by part:

(dy)/(du)=5*1/udydu=51u

(du)/(dx)=7+6*1/xdudx=7+61x

Aggregating them:

(dy)/(dx)=5/u(7+6/x)=5/(7x+6ln(x))(7+6/x)=color(green)((35+30/x)/(7x+6ln(x)))dydx=5u(7+6x)=57x+6ln(x)(7+6x)=35+30x7x+6ln(x)