x+1x−1\frac{x+1}{x-1}x−1x+1
x2−1x2+1\frac{x^{2}-1}{x^{2}+1}x2+1x2−1
x−1x+1\frac{x-1}{x+1}x+1x−1
x2+1x2−1\frac{x^{2}+1}{x^{2}-1}x2−1x2+1