((xy+2)(xy-2)-2x²y²+5(xy-y)²)÷(2xy)解,得：==(x^2y^2-4-2x²y²+5x^2y^2-10xy^2+5y^2)÷(2xy)==(4+4x^2y^2-10xy^2+5y^2)÷(2xy)==2/xy+2xy-5y+2.5y/x