根号x+根号y-（根号xy+x）乘根号1/x
=根号x+根号y-根号xy乘根号1/x-x乘根号1/x
=根号x+根号y-根号y-根号x
=0根号xy乘根号1/x-x 这一步 我不懂-x在根号里面吗？分配律啊