已知x+y+z=3,且(x-1)^3+(y-1)^3+(z-1)^3=0,求证：x,y,z中至少有一个为1.

已知x,y,z都是正数,且xyz=1,求证：x^2/(y+z)+y^2/(x+z)+z^2/(x+y)≥3/2 已知方程组{X+Y-7Z=0(1)3X-2Y-Z=0(2)且Z不等于0求X:Y:Z 已知x:y:z=2:3:4,且x-y+z=36,求x+y+z的值. 已知x:y:z=2:3:4且x+z-y=36求x+y+z的值 已知x:y:z=2:3:4,且x+z-y=36.求x+y+z的值 已知x:y:z=2:3:4,且x+y+z=18.求x、y、z的值. 已知（x+y-xy）/(x+y+2xy)=(y+z-2yz)/(y+z+3yz)=(z+x-3zx)/(z+x+4zx),且2/x=3/y-1/z,则xyz=? 已知x（1/y+1/z)+y(1/x+1/z)+z(1/x+1/y)+3=0,且x分之1+y分之1+z分之1不等于0,求x+y+z的值.要有过程! 已知x(1/y+1/z)+y(1/x+1/z)+z(1/x+1/y)+3=0 且1/x+1/y+1/z不等于零,求x+y+z的值 已知x(1/y+1/z)+y(1/x+1/z)+z(1/x+1/y)+3=0,且1/x+1/y+1/z不等于0,求x+y+z的植? 已知x,y,z∈R+,且x+y+z=3,求证：x^2/（y^2+z^2+yz）+y^2/(x^2+z^2+zx）+z^2/(x^2+y^2+xy)≥1 已知x、y、z都不为0,且4x-3y-3z=0,x-3y+z=0,求x:y:z 已知x/2=y/3=z/4,且x+y+z不等于0,求2x+3y-4z/x+y+z的值 已知方程组{2x-3y+z=0 且x*y*z不等于0 求 x：y：z {3x-2y-6z=0 已知x=y/3=z/5.且x+y-2z不等于0.求2x+3y-z/x+y-2z的值是多少 已知x/2=y/3=z/4,且x+y+z不等于0,求2x+3y-4z/x+y+z的值 已知x+y/2=y+z/3=z+x/4,且x+2y+z=12,求x-2y+z的值 已知X+Y/2=Y+Z/3=Z+X/4,且2X+4Y+6Z=120,求X,Y,Z的值