Simplify: x+3x−1−x−3x+1\frac{x+3}{x-1} - \frac{x-3}{x+1}x−1x+3−x+1x−3 (assume x≠±1x \neq \pm 1x=±1).
8xx2−1\frac{8x}{x^2-1}x2−18x
8x2−1\frac{8}{x^2-1}x2−18
2x2−1\frac{2}{x^2-1}x2−12
8x−6x2−1\frac{8x-6}{x^2-1}x2−18x−6