解下列三元一次方程组(1)y=2x-7(2)4x+9y=125x+3y+2z=23y-2z=13x-4z=47x+5z=19/4(3)4x-9z=17(4)2x+4y+3z=93x+y+15z=183x-2y+5z=11x+2y+3z=25x-6y+7z=13

Question

解下列三元一次方程组
(1)y=2x-7 (2)4x+9y=12
5x+3y+2z=2 3y-2z=1
3x-4z=4 7x+5z=19/4
(3)4x-9z=17 (4)2x+4y+3z=9
3x+y+15z=18 3x-2y+5z=11
x+2y+3z=2 5x-6y+7z=13

Answer 1

(1)y=2x-7 (2)4x+9y=12
5x+3y+2z=2 3y-2z=1
3x-4z=4 7x+5z=19/4
11x+(3x-4)/2=23 4x+6z=9
12.5x=25 22z=44,z=2,x=-3/4,y=5/3
x=2
y=-3,z=0.5
(3)4x-9z=17
3x+y+15z=18
x+2y+3z=2
5x+27z=34
17x=85
x=5
y=-2
z=1/3
(4)2x+4y+3z=9
3x-2y+5z=11
5x-6y+7z=13
8x+13z=31
4x+8z=20,x=5-2z
40-3z=31
z=3
x=-1
y=0.5