已知3x+y+2z=28,5x-3y+z=7,求x+y+z的值。
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- 2023-12-07 07:57:21
已知3x+y+2z=28,5x-3y+z=7,求x:y:z的值.
4:5:7 绝对正确!!!初一 数学 三元一次方程
可以用待定系数法,设a*(3x+y+2z)+b*(5x-3y+z)=x+y+z 3a+5b=1,a-3b=1,2a+b=1 a=4/7,b=-1/7 x+y+z=153x+y+2z=28 5x-3y+z=7 x+y+z=? 全部过程
3x+y+2z=28 ① 5x-3y+z=7 ② ①-②×2,得 -7x+7y=14 7y=14+7x y=2+x 将y=2+x带入②,得 5x-6-3x+2=7 2x+z=13 z=13-2x 将y=2+x,z=13-2x代入x+y+z,得 x+y+z=15 望采纳。谢谢。(步骤你可以省略一部分的。)已知3x+y+2z=28,5x-3y+z=7,求x+y+z的值
3x+y+2z=28 5x-3y+z=7 10x-6y+2z=14 7x-7y=-14 x-y=-2......-x+y=2 y=x+2 3x+y+2z=3x+x+2+2z=4x+2z+2=28 2x+z=13 -x+y+2x+z=2+13 x+y+z=15 或者...........................................................................................................................................3x+y+2z=28 ① 5x-3y+z=7 ②,求x+y已知X,y,Z满足3X+y+2Z=28,5X-3y+Z=7,求X+y+Z的值
4(3x+y+2z)-(5x-3y+z) =12x+4y+8z-5x+3y-z =7x+7y+7z =7(x+y+z) =105 所以,x+y+z=15展开全文阅读
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