2x+3y-4z=0,3x+4y+5z=0,求x+y-z/x-y+z的值

问题描述:

2x+3y-4z=0,3x+4y+5z=0,求x+y-z/x-y+z的值

2x+3y-4z=0,
3x+4y+5z=0
两式把z看作已知,可解得
x=-31z
y=22z
(x+y-z)/(x-y+z)=(-31z+22z-z)/(-31z-22z+z)=5/26