数学题在线解答：三元一次方程组；(1)X+Y+Z=0,4X+2Y+Z=0,Z=2;(2)9X+3Y+Z=0,X-Y+Z=0,Z=-3,
问题描述：
数学题在线解答：三元一次方程组；(1)X+Y+Z=0,4X+2Y+Z=0,Z=2;(2)9X+3Y+Z=0,X-Y+Z=0,Z=-3,
(3)4X+2Y+Z=5,4X-2Y+Z=1Z=-1;(5)5X+2Y+Z=12,4X+3Y+Z=13,Z=3
答
1)
X+Y+Z=0,
4X+2Y+Z=0,
Z=2
则
x+y=-2
2x+y=-1
x=1
y=-3
z=2
(2)9X+3Y+Z=0,
X-Y+Z=0,
Z=-3,
则
3x+y=1
x-y=3
x=1
y=-2
z=-3
3)
4X+2Y+Z=5,
4X-2Y+Z=1
Z=-1
则
2x+y=3
2x-y=1
x=1
y=1
z=-1
(5)
5X+2Y+Z=12,
4X+3Y+Z=13,
Z=3
则
5x+2y=9
4x+3y=10
7x=7
x=1
y=2
z=3