代数题 3^X=4^Y=12^Z 证明Z=XY／X+Y

试证明(x+y-2z)+(y+z-2x)+(z+x-2y)=3(x+y-2z)(y+z-2x)(z+x-2y) 证明 当x+y+z=1时,x/yz+y/xz+z/xy≥9 设x,y,z≥0,x+y+z=3,证明:√x+√y+√z≥xy+yz+zx 用放缩法证明√(x^2+xy+y^2)+√(y^2+yz+z^2)+√(z^2+zx+x^2)>=(3/2)(x+y+z x=y/z=z/3,x+y+z ＝12,求2x+3y+4z是多少, 已知x^3+y^3-z^3=96,xyz=4,x^2+y^2+z^2-xy+xz+yz=12,则x+y-z等于 xy/x+y=6/5 yz/y+z=12/7 xz/x+z=4/3 求x和y和z 若x/3=y=z/4,且xy+xz+yz=76,求2x*x+12y*y+9z*z的值 解方程组 ｛xy\X+Y=12\7 ,YZ\Y+Z=6\5 ,XZ\X+Z=4\3 若xy-z不等于0,且(y+x)/x=(z+x)/y=(y+x)/z,求[(y+z)(z+x)(x+y)]/xyz的值? 已知三个数x,y,z,满足xy/x+y=-2，yz/y+z=4/3,zx/z+x=-4/3,求(xyz)/(xy+yz+ (x+y-z)(x-y+z)=