(x根号y-y根号x）除以根号xy
=根号(x^2y-根号(xy^2) / 根号(xy)
=根号[(x^2y)/(xy)] - 根号[(xy^2)/(xy)]
=根号x - 根号y=根号(x^2y-根号(xy^2) / 根号(xy)=根号[(x^2y)/(xy)] - 根号[(xy^2)/(xy)]这是什么意思啊？