(y-z)/(y+z)=a,(z-x)/(x+z)=b,(x-y)/(x+y)=c,求a+b+c+abc的值
问题描述：
(y-z)/(y+z)=a,(z-x)/(x+z)=b,(x-y)/(x+y)=c,求a+b+c+abc的值
答
4XYZ/（X+Y)(Y+Z)(Z+X)
纯粹化简问题