(x^3 + y^3)/(x^5 + y^5)
2 2
x + y - x*y
-----------------------------
4 4 2 2 3 3
x + y + x *y - x*y - y*x 2 2
x + y - x*y
-----------------------------
4 4 2 2 3 3
x + y + x *y - x*y - y*x