已知实数x、y、z满足x^2+y^2+z^2=4 则(2x-y)^2+(2y-z)^2+(2z-x)^2的最大值是A.12 B.20 C.28 D.36主要是xy+yz+zx的最小值怎么求,

已知实数x y z满足x/(x+1)=y/(y+2)=z/(z+3)=(x+y+z)/3,求x+y+z的值 已知实数x y z满足x/(x+1)=y/(y+2)=z/(z+3)=(x+y+z)/3,求x+y+z的值 已知实数x,y,z,满足那么x+y=6,z^2=xy-9,求(x+y)^z 已知实数x,y,z满足x+y+z=2根号x-1+2根号y-1+2根号z-1求X+2Y+3Z 已知实数x,y,z满足关系式2x-3y-z=0,x-2y+z=0,求x比y比z的值 已知x,y,z均为实数,且满足:x+2y-z=6,x-y+2z=3.求x+y+z的最小值 已知实数xyz满足x/(x+1)=y/(y+2)=z/(z+3)=(x+y+z)/3求x+y+z的值 已知三个实数x,y,z满足条件(z-x)^2-4(x-y)(y-z)=0,求证:x,y,z成等差数列 已知实数 x y z 满足x+y-z=0 ,3x-y+2z=0 则x :y :z 已知实数x,y,z满足2｜x-y｜+√2y+z+z2-z+1/4=0求x+y+z的值 已知实数xyz满足x/y+z+y/z+x+z/x+y=1求x^2/y+z+y^2/z+x+z^2/x+y的值 纠正下！：已知实数xyz满足（x/y+z）+（y/z+x）+（z/x+y）=1求（x^2/y+z）+（y^2/z+x）+（z^2/x+y）的值 已知实数x,y,z满足x=6-y,z^2=xy-9,求证：x=y 已知实数X,Y,Z,满足X^2-2X+Y=Z-1,且X+Y^2+1=0,试比较X,Y,Z的大小. 已知实数x,y,z满足x=6-y,z^2-4z+4=xy-9,求x,y,z的值 已知实数x,y,z满足x=6-y,z^2-4z+4=xy-9,求x,y,z的值. 已知实数x,y,z满足x+y+z=1,x^2+y^2+z^2=1/2求X,Y,Z∈{0,2/3},已知实数x,y,z满足x+y+z=1,x^2+y^2+z^2=1/2求证X,Y,Z∈{0,2/3}, 已知实数x,y,z,满足x²+4y²+根号-z²=2x+4y-2,求x+2y-z的平方 已知x,y,z为正实数,满足x-y+2z=0,求y²/(xz)的最小值