# Math Help - Can't find derivative

1. ## Can't find derivative

I can't find the derivative of:

f(x) = (2x^2) / (x^2-1)

Having a hard time with this one.

2. Originally Posted by thekrown
I can't find the derivative of:

f(x) = (2x^2) / (x^2-1)

Having a hard time with this one.

First way: quotient rule: $f'(x)=\frac{4x(x^2-1)-2x(2x^2)}{(x^2-1)^2}=\frac{-4x}{(x^2-1)^2}$

Second way: first write $f(x)=2+\frac{2}{x^2-1}$ and now we only need the derivative of $\frac{1}{x^2}$ :

$f'(x)=\frac{-4x}{(x^2-1)^2}$

Tonio

3. Quotient rule! Oh yes I remember this and had forgotten it just as quickly. Yes I believe it is uv'-vu' / 2v or something... I will look into this and try this again. Thanks.