方程组 3X+2Y+Z =13X+Y+2Z =72X+3Y-Z =12

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方程组 3X+2Y+Z =13X+Y+2Z =72X+3Y-Z =12
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方程组 3X+2Y+Z =13X+Y+2Z =72X+3Y-Z =12
方程组
3X+2Y+Z =13
X+Y+2Z =7
2X+3Y-Z =12

方程组 3X+2Y+Z =13X+Y+2Z =72X+3Y-Z =12
3X+2Y+Z =13 (1)
X+Y+2Z =7 (2)
2X+3Y-Z =12 (3)
(1)+(3)得5X+5Y=25 (4)
(3)×2+(2)得5X+7Y=31 (5)
(5)-(4)得2Y=6,∴Y=3
代入(4)得X=2
代入(2)得Z=1

X+Y+2Z=7乘以3减去3X+2Y+Z =13得 Y+5Z=8 2X+3Y-Z =12 乘以5得10X+3Y-5Z=60 用10X+3Y-5Z=60加Y+5Z=8 得X=2 Z=1 Y=3