3x+y+2z=28,5x-3y+z=7,试求x+y+z的值!

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3x+y+2z=28,5x-3y+z=7,试求x+y+z的值!
3x+y+2z=28,5x-3y+z=7,试求x+y+z的值!

3x+y+2z=28,5x-3y+z=7,试求x+y+z的值!
条件不够,或者说条件给错了,因为在用X代了Y,Z后代入X+Y+Z获得的结果是（22X-53）/6,不能完全消去X,也就是说X+Y+Z的数值是随着X（或Y或Z）的值变化的,没有固定值.

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
另一种做法
3x+y+2z=28...

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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
另一种做法
3x+y+2z=28 ①
5x-3y+z=7 ②，求x+y+z
由①得：y=28-3x-2z ③，
代入②得：5x-3（28-3x-2z）+z=7
x=（91－7 z）／14
代入③得：y=28-3（91－7 z）／14-2z
y=（119-7z）／14
x+y=（91－7 z）／14+（119-7z）／14
x+y=15-z
x+y+z=15

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x+y-z=3 y+z-x=5 z+x-y=7 求x,y,z x/2=y/3=z/5 x+3y-z/x-3y+z 三元一次方程解 1.{x+y-z=5 {3x+2y+z=2 {2x-2y+z=-31.{x+y-z=5 2.{9x-5y+x=-6 3.{x-y=3 4.{x+y=3 5.{4x-2y+z=7{3x+2y+z=2 {9x+y-2z=3 {x+z=7 {y+z=4 {2x-y-3z=28{2x-2y+z=-3 {-9x+3y-5z=0 {y-z=6 {z+x=5 {x+y-2z=13 {x+y+z=1;x+3y+7z=-1;z+5y+8z=-2 已知(x+y)(x+z)=x,(y+z)(y+x)=2y,(z+x)(z+y)=3z,求x,y,z 试证明(x+y-2z)+(y+z-2x)+(z+x-2y)=3(x+y-2z)(y+z-2x)(z+x-2y) 已知x-y/x+y=y+z/2(y-z)=z+x/3(z-x),求证8x+9y+5z=0THX.. 若X:Y:Z=5:6:7那么(Y-X):(Y+Z)和(X+2Y+3Z):(3X+2Y+Z) x+Y+Z=1 X+3Y+7Z=-1 X+5Y+8Z=2x+Y+Z=1X+3Y+7Z=-1X+5Y+8Z=2 3x-y=-7,y+2z=2,2x-2z=-5 求x,y,z x+y+z=0,3x-2y-2z=5,y-z=2x-7 X-Y-Z=0 X+Y-3Z=4 2X-5Y+7Z=21 2x+5y+4z=6,3x+y-7z=-4,x+y-z=? 3x+7y+4z=35,x+5y+2z=40,x+y+z=( ) {x+y+z=1 {x+3y+7z=-1 {x+5y+8z=2 {x+y+z=1 {x+3y+7z=2 {x+5y+19z=4 已知2x+5y+4z=6 3x+y-7z=-4求x+y-z 5x+3y+2z=2011 4x+6y+7z=2012 求x+y+z