x:y=4:7,x:z=3:5,x-2y+3z=30

2x+5y+4z=6,3x+y-7z=-4,x+y-z=? 2x+5y+4z=0,3x+y-7z=0,则x+y-z=? 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 x/2=y/3=z/5 x+3y-z/x-3y+z x-y-z=-1 3x+5y+7z=11 4x-y+2z=-1 分别求出x=?y=?z=? 已知x+4y+3z=3x-2y-5z=0,求x+2y-z/2x-3y+7z的值 1.x+y+z=30,3x+y-z=50,x,y,z为非负数,求5x+4y+2z取值范围. {5x-3y+z=2{5x+2y-4z=3{-5x+y-z=2 {x-y-z=-1{3x+5y+7z{4x-y+2x=- 试证明(x+y-2z)+(y+z-2x)+(z+x-2y)=3(x+y-2z)(y+z-2x)(z+x-2y) 若4x-3y-6z=0,x+2y-7z=0,求代数式5x*5x+2y*2y-z*z/2x*2x-3y*3y-10z*10 {x+y+z=1;x+3y+7z=-1;z+5y+8z=-2