2 1 1 x^2+y^2
----- : (--- – ---)^2 – ------------- =
xy x y (x–y)^2
2 y–x x^2+y^2
= ---- : (-------)^2 – ------------- =
xy xy (x–y)^2
2•(xy)^2 x^2+y^2
= --------------- – ------------- =
xy•(y–x)^2 (x–y)^2
2xy x^2+y^2 2xy–x^2–y^2
= ---------- – ------------ = ------------------- =
(y–x)^2 (y–x)^2 (y–x)^2
x^2–2xy+y^2 (y–x)^2
= – -------------------- = – ---------- = –1
(y–x)^2 (y–x)^2