(x-y+x+y)/(x^2-y^2)*((x-y)^2/2x)
=2x/(x-y)(x+y)*((x-y)^2/2x)
=(x-y)/(x+y)
x=根号3,y=负根号2
原式=（根号3+根号2）/（根号3-根号2）
= （根号3+根号2）^2/(3-2)
=（3+2+2根号6）/1
=5+2根号6