Which expression is equivalent to xx−1−xx+1\frac{x}{x-1} - \frac{x}{x+1}x−1x−x+1x?
2xx2−1\frac{2x}{x^2-1}x2−12x
2x2−1\frac{2}{x^2-1}x2−12
x2x2−1\frac{x^2}{x^2-1}x2−1x2
000