（1/x-y+1/x+y）÷x^2 y^2/x^2-y^2＝（2x)/(x^2-y^2)÷(x^2 y^2)/(x^2-y^2)＝（2x)/(x^2-y^2)÷(x^2-y^2)/(x^2 y^2)＝2/(xy^2)当x=3,y=-√2 时2/(xy^2)＝2/(3*2)＝1/3江苏吴云超祝你学习进步