已知根号下27-10倍根号2=a-b根号2
根号下(27-10倍根号2)
=根号下 [5²+(根号2)²-10倍根号2]
=5 -根号2
则,a=5 ,b=1
a-b分之a+b
=(5-1)分之(5+1)
=4分之6
=2分之3