I'm new at this, so...

$\displaystyle yln{x}\ln{y}dx+dy=0$

then, making it a function:

$\displaystyle f(x,y)=\frac{dy}{dx}= -yln{x}\ln{y} $

$\displaystyle \frac{\partial{f}}{\partial{y}}= ?$

any help (and further explanations) will be great...

thanks in advance ^^