X y+x-y = 2 radical formula 2 = => (x y+x-y) 2 = 8 = = > x^2y+x^-2y+2=8===>； x^2y+x^-2y=6

(x^y-x^-y)^2=x^2y+x^-2y-2=6-2=4==>； x^y-x^-y=2

(a^ 1/2-b^ 1/2)/(a^ 1/2+b^ 1/2)+(a^ 1/2+b^ 1/2)/(a^ 1/2-b^ 1/2)=[(a^ 1/2-b^ 1/2) ^2+(a^ 1/ 2+b^ 1/2)^2]/(a^ 1/2-b^ 1/2)(a^ 1/2+b^ 1/2)=2(a+b)/(a-b)