# Homework Help: Finding the derivative, quotient rule with natural log function.

1. Feb 19, 2012

### HHenderson90

1. The problem statement, all variables and given/known data

Find y' of
y= 1-3ln(7x)/x^4

2. Relevant equations

3. The attempt at a solution
I used the quotient rule and got:
y'=x^4*d/dx(1-3ln(7x)-(1-3ln(7x)*d/dx(x^4)/(x^4)2

which is: x^4*(0-3*1/7x*7)-(1-3ln(7x))*4x^3/x^8
simplified to: 3x^4/x-1+3ln(7x)*4x^3
3x^3-4x^3+12x^3ln(7x)/x^8
take out the x^3 from the denominator and the numerator and I get the answer:

y=-1+12ln(7x)/x^5
The website I use to do my calculus homework says this is wrong, where is my error?

2. Feb 19, 2012

### Dick

You dropped a minus sign. You should get -3x^3-4x^3. Not 3x^3-4x^3.