y2+11−2xy\frac{y^{2}+1}{1-2 x y}1−2xyy2+1
y2−11−2xy\frac{y^{2}-1}{1-2 x y}1−2xyy2−1
y2−12−2xy\frac{y^{2}-1}{2-2 x y}2−2xyy2−1
y2−1−3xy\frac{y^{2}-1}{-3 x y}−3xyy2−1