解方程组:3x+y=9和10x-11y=30,x+2y+4z=17和2x+y+z=7和3x+y+2z=11(写过程)

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解方程组:3x+y=9和10x-11y=30,x+2y+4z=17和2x+y+z=7和3x+y+2z=11(写过程)解方程组:3x+y=9和10x-11y=30,x+2y+4z=17和2x+y+z=7

解方程组:3x+y=9和10x-11y=30,x+2y+4z=17和2x+y+z=7和3x+y+2z=11(写过程)
解方程组:3x+y=9和10x-11y=30,x+2y+4z=17和2x+y+z=7和3x+y+2z=11(写过程)

解方程组:3x+y=9和10x-11y=30,x+2y+4z=17和2x+y+z=7和3x+y+2z=11(写过程)
3x+y=9 y=9-3x代入:
10x-11y=30
10x-11(9-3x)=30
10x-99+33x=30
43x=129
x=3
y=9-3x=9-3*3=0
所以:x=3,y=0
x+2y+4z=17 (1)
2x+y+z=7 (2)
3x+y+2z=11 (3)
(3)-(2):
x+z=4 ,z=4-x (4)
(1)-2*(2):
x+2y+4z-4x-2y-2z=17-7*2
-3x+2z=3 (5)
(4)代入(5):
-3x+2(4-x)=3
-3x+8-2x=3
5x=5
x=1,代入:(4)
z=4-x=4-1=3,代入(2):
2*1+y+3=7
y=2
所以:x=1,y=2,z=3