1/根号6-根号5+2/根号5+根号2+4/根号6+根号2
=1/根号6+4/根号6-根号5+2/根号5+根号2+根号2
=5/根号6-5/根号5+2/根号5+根号2+根号2
=5/根号6-3/根号5+2*根号2