упростите выражение x/x+y + y/x-y

x. +. y
------- ---------- =
x+y. x-y


x(x-y) +y(x+y)
--------------------- =
(x+y)(x-y)

x^2 -xy +yx+y^2
------------------------ =
X^2 -y^2

x^2 +y^2
---------------
x^2 - y^2