# Thread: Using Quotient Rule to find y'

1. ## Using Quotient Rule to find y'

Hey guys!

The following question asks me to find y' via the quotient rule.

I know the quotient rule is:

$[f'(x)*g(x) - f(x)*g'(x)]/g(x)^2$

so i got:

$[3x^2+2]*[(4x^2-ln(x)^2] - [x^3-2x]*2[4x^2-ln(x)]$ divided by $[4x^2-ln(x)]^4$

what i don't understand is, in the solution key, they throw $(8x-1/x)$ in there.... where do they get that from?

2. Is...

$\displaystyle \frac{d}{dx} (4\ x^{2} - \ln^{2} x)^{2} = 2\ (4\ x^{2} - \ln^{2} x)\ (8\ x -\frac{2}{x}\ \ln x)$

Kind regards

$\chi$ $\sigma$

3. thanks!