解方程组3x+y+z=6,x+3y+z=5,x+y+3z=9{3x+y+z=6{x+3y+z=5{x+y+3z=9

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解方程组3x+y+z=6,x+3y+z=5,x+y+3z=9{3x+y+z=6{x+3y+z=5{x+y+3z=9

解方程组3x+y+z=6,x+3y+z=5,x+y+3z=9{3x+y+z=6{x+3y+z=5{x+y+3z=9
解方程组3x+y+z=6,x+3y+z=5,x+y+3z=9
{3x+y+z=6
{x+3y+z=5
{x+y+3z=9

解方程组3x+y+z=6,x+3y+z=5,x+y+3z=9{3x+y+z=6{x+3y+z=5{x+y+3z=9
3x+y+z=6
x+3y+z=5
x+y+3z=9
全加起来,得
3x+y+z+x+3y+z+x+y+3z=6+5+9
5x+5y+5z=20
x+y+z=4
3x+y+z-(x+y+z)=6-4
2x=2,x=1
同理将2、3式减x+y+z=4
得y=0.5,z=2.5