3x+y-z=0
12x+4y-4z=0和x+2y-4z=0相减的11x+2y=0
11x+2y=0得x/y=-2/11
3x+y-z=0
6x+2y-2z=0和x+2y-4z=0相减的5x+2z=0
5x+2z=0得x/z=-2/5
所以x:y:z=-2:11:5