2x+y-z=-3,3x+2y+z=2,x-5y+2z=17

试证明(x+y-2z)+(y+z-2x)+(z+x-2y)=3(x+y-2z)(y+z-2x)(z+x-2y) x/2=y/3=z/5 x+3y-z/x-3y+z {x+y+z=1;x+3y+7z=-1;z+5y+8z=-2 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 x=y/z=z/3,x+y+z ＝12,求2x+3y+4z是多少, 如果|x+y+z-6|+|2x+3y-z-12|+|2x-y-z|=0求x,y, (4x-2y-z)-{5x[8y-2y-(x+y)]-x+(3y-10z)]=? kuai 4x-5z=17 3x+y+15z=18 x+2y+3z=2 x+2y+4z=17 2x+y+z=7 3x+y+2z=11 2x-y+2z=-17 3x+y-3z=-4 x+y+z=6 x+y=z 2x-3y+2z=5 x+2y-z=3 解方程组{z=x+y 3x-2y-2z=-5 2x+y-z=3