已知：x y-z=0 求证：X^3 8y^3=z^3-6xyz

已知x,y,z满足xyz=1,求证x^3/(x+y)+y^3/(y+z)+z^3/(z+x)大于等于3 已知xyz属于R+,x+y+z=1,求证x^3/(y(1-y))+y^3/(z(1-z))+z^3/(x(1-x))大于 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4x-3y+z=0,x+2y-8z=0,xyz不等于0,求x+y-z/x-y+2z的值 已知方程组4x-y+3z=0 2x+y+6z=0且xyz不等于0,则x/y+y/z+z/x是多少 已知X,Y,Z为3个互不相等的实数,且X+1/Y=Y+1/Z=Z+1/Z求证(xyz)^2=1 已知2^x=3^y=6^z,xyz不等于0,求证：(1/x)+(1/y)+(1/z)=0…… 已知x,y,z都是正数, 且x^3+y^3+z^3=3xyz, 求证：x=y=z. 求教初二数学难题已知：(1/x+1/y+1/z)^(1/3)=1/x+1/y+1/z,且xyz>0,求证：1/x+1/y 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 已知x+y-z/z=x-y+z/y=-x+y+z/x,且xyz不等于0,求分式[(x+y)(x+z)(y+z)]/xyz 已知xyz满足|3x-2y+z|+|2x+y+2z|=0（xyz不等于o）求x+y除以z