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XYZ≠O,且2X-Y-Z=0,X+2Y-5Z=0,求代数式(X-Y)/(Y+Z)的值
请大大门写下简单的过程,谢谢

2X-Y-Z=0,X+2Y-5Z=0
得到X=1.4Z,Y=1.8Z
(X-Y)/(Y+Z)=-0.4Z/2.8Z=-1/7

2X-Y-Z=0,X+2Y-5Z=0,
x=1.4z y=-2.2z XYZ≠O z≠0
(x-y)/(y+z)=(1.4z+2.2z)/(-2.2z+z)=-3