已知3x+7y+z=3.15,4x+10y+z=4.2求x+y+z的值 将原方程组整理得2(x+3y)+(x+y+z)=3.15,(1)3(x+3y)+(x+y+z)=4.2(2) (1)×3,得6(x+3y)+3(x+y+z)=9.45,(3) (2)×2,得6(x+3y)+2(x+y+z)=8.40,(4) (3)-(4),得x+y+z=1.05 仿照上述解法,
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已知3x+7y+z=3.15,4x+10y+z=4.2求x+y+z的值 将原方程组整理得2(x+3y)+(x+y+z)=3.15,(1)
3(x+3y)+(x+y+z)=4.2(2) (1)×3,得6(x+3y)+3(x+y+z)=9.45,(3) (2)×2,得6(x+3y)+2(x+y+z)=8.40,(4) (3)-(4),得x+y+z=1.05 仿照上述解法,已知方程组x+y+z=11,x-3y-z=1 试求x+0.5z的值
已知方程组x+y+z=11,x-3y-z=1
将原方程组整理得(y+0.5z)+(x+0.5z)=11,(1)
-3 (y+0.5z)+(x+0.5z)=1 (2) 【(-3 y-1.5z)+(x+0.5z)=1
(1)×3+(2)
得4(x+0.5z)=12
x+0.5z=3
【关键是把方程转化为要求的x+0.5z】
x-3y-z=1
原方程可化为(x+y+z)-2(2y+z)=1(1)
∵x+y+z=11
∴2y+z=5
∴x+0.5z=(x+y+z)-0.5(2y+z)=11-0.5×5=8.5
我也做不来啊
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