Given that $f(x) = \dfrac{x}{x+ (2/x)}$
The derivative function is given by $f'(x) = \dfrac{Ax^2 + Bx + C}{(x^2+D)^2}$
where
$A=$
$B=$
$C=$
$D=$
From rearranging the original equation, I can get $D=2$, $C=0$ and $A=0$, but I cant seem to find $B$. Maybe someone could help?
EDIT: I found the answer to be $4$, but don't see how this makes sense, since I can only clearly see how $-2$ would work.