第一题就不用我说了吧， 2.（1）(x/2y)^2 * y/2x - x/y^2 / 2y^2 /x
=x^2/4y^2 * y/2x - x/y^2 *x/2y^2
=x/8y -x^2/2y^4
=xy^3-4x^2 / 8y^4
好累吖
