2x=-y,则分式xy/x方-y方的值为?
问题描述：
2x=-y,则分式xy/x方-y方的值为?
答
xy/(x^2-y^2) =(-2x*x)/(x^2-4x^2) =-2x^2/-3x^2 =2/3
答
2x=-y y=-2x xy/(x方-y方) =(-2x方)/(x方-4x方) =2/3