解不等式组x+y=-3;y+z=2;x+z=7
试证明(x+y-2z)+(y+z-2x)+(z+x-2y)=3(x+y-2z)(y+z-2x)(z+x-2y)
解方程:{2x+3y+z=7,x+y+z=4,3x+y-z=-4
解三元一次方程:x+y-z=0,2x+y+z=7,x-3y+z=8
{x+y+z=1;x+3y+7z=-1;z+5y+8z=-2
(x+y-z)(x-y+z)=
x/2=y/3=z/5 x+3y-z/x-3y+z
4X-5z=17 3x+y+15z=18 x+2y+3z=2 解三元一次不等式要过程
解方程一;{x+y-z=6,x-3y+2z=1,3x+2y-z=-7.②{3x+4z=7,2x+3y+z=9,5x-9y
解方程组:2x+3y+4z=20,x+y+z=7
2x+3y+4z=20;x+y+z=7 的解
已知x,y,z 大于0,x+y+z=2,求证 xz/y(y+z)+zy/x(x+y)+yx/z(z+x)大于等于2/3
解方程组2x+y-z=7 x+y+z =1 2x-y-z=5