Factor $$\frac{y-x}{x^{2}$$$-y^{2}$}.
$\frac{y-x}{x+y}$
$\frac{-1}{x+y}$
$\frac{y-x}{x-y}$
$\frac{1}{x+y}$
$$\frac{1}{x^{2}$$$-y^{2}$}
If , and , what is the value of ?
, and 
, what is the value of 
?