已知x+y+z=0求证x*x*x+y*y*y+z*z*z=3xyz

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已知x+y+z=0求证x*x*x+y*y*y+z*z*z=3xyz已知x+y+z=0求证x*x*x+y*y*y+z*z*z=3xyz已知x+y+z=0求证x*x*x+y*y*y+z*z*z=3xyz题

已知x+y+z=0求证x*x*x+y*y*y+z*z*z=3xyz
已知x+y+z=0求证x*x*x+y*y*y+z*z*z=3xyz

已知x+y+z=0求证x*x*x+y*y*y+z*z*z=3xyz
题意即要求证X^3+Y^3+Z^3-3XYZ=0
证明如下:x^3+y^3+z^3-3xyz =(x+y+z)(x^2+y^2+z^2-xy-yz-zx)
因为X+Y+Z=0,所以上式等于0.所以x^3+y^3+z^3-3xyz=0,X^3+Y^3+Z^3=3XYZ,得证.