1) (х+у/х - 2х/х-у) * у-х/х^2+у^2 = 2) 1/а-2 - 4а/а^2-4 * (1/а-1 - 1/а^2-а) =

1) (x+y)(x-y)-2x^2)/(x(x-y)*(y-x)/(x^2+y^2)=(x^2-y^2-2x^2)/x (x^2+y^2) =(x^2+y^2)/x(x^2+y^2)=1/x
2. (a+2-4a)/(a-2)(a+2))*(a-1)/a(a-1)=(2-3a)*a/(a-2)(a+2))=(2a-3a^2)/(a^2-4)