Which expression is equivalent to x−1−y−1x−2−y−2\frac{x^{-1} - y^{-1}}{x^{-2} - y^{-2}}x−2−y−2x−1−y−1?
xyx+y\frac{xy}{x+y}x+yxy
x+yxy\frac{x+y}{xy}xyx+y
x+yx+yx+y
1x+y\frac{1}{x+y}x+y1