x+Y+Z=1 X+3Y+7Z=-1 X+5Y+8Z=2

{x+y+z=1;x+3y+7z=-1;z+5y+8z=-2 x-y-z=-1 3x+5y+7z=11 4x-y+2z=-1 分别求出x=?y=?z=? {5x-3y+z=2{5x+2y-4z=3{-5x+y-z=2 {x-y-z=-1{3x+5y+7z{4x-y+2x=- （1）3x+4z=7;2x+3y+z=9;5x-9y+7z=8 (2)3x+4y+z=14;x+5y+2z=17;2x+ 已知x:y:z=4:5:7,求:(1)2x+3y+z/5z; (2)x+y/y+z. x/2=y/3=z/5 x+3y-z/x-3y+z 三元一次方程组：1、3x+4z=7 2x+3y+z=9 5x-9y+7z=8 2、2x+4y=3z 3x-2y+5z 5 x+2y-z=1 3x-3y+z=2 3x+3y+z=7 解方程组2x+y-z=7 x+y+z =1 2x-y-z=5 3x+2y+z=14 ,x+y+z=10,z+2x+3y=1 5 x+y+z=2 x-3y+2z=1 2x+2y+z+5 要具体步骤.. 试证明(x+y-2z)+(y+z-2x)+(z+x-2y)=3(x+y-2z)(y+z-2x)(z+x-2y)