你的题应是(y-z)/(y+z)=a (z-x)/(z+x)=b (x-y)/(x+y)=c吧?
若是的话:答案是0
过程如下:
a+b+c+abc=[(y-z)(x+z)(x+y)+(z-x)(y+z)(x+y)+(x-y)(y+z)(x+z)+(y-z)(z-x)(x-y)]/[(y+z)(x+z)(x+y)]={(x+y)[(y-z)(x+z)+(z-x)(y+z)]+(x-y)[(y+z)(x+z)+(y-z)(z-x)]}/[(y+z)(x+z)(x+y)]=[2z(x+y)(y-x)+2z(x-y)(x+y)]/[(y+z)(x+z)(x+y)]=0