x-2y-3z=0 (1)
2x+y-2z=0(2)
(1)+(2)*2
x-2y-3z+4x+2y-4z=0
5x-7z=0
5x=7z
x:z=7:5
(2)-(1)*2
2x+y-2z-2x+4y+6z=0
5y+4z=0
5y=-4z
y:z=(-4):5
所以x:y:z=7:(-4):5