chứng minha) (a2+b2+c2)(x2+y2+z2)-(ax+by+cz)2=(bx-ay)2+(cy-bz)2+(az-cx)2b) (a2+b2)(x2+y2)-(ax+by+cz)2=(ax-by)2+(bx+ay)2c) nếu (x-y)2+(y-z)2+(z-x)2=(y+z-2x)2+(z+x-2y)2+(x+y-2z)2 thì...
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chứng minh
a) (a2+b2+c2)(x2+y2+z2)-(ax+by+cz)2=(bx-ay)2+(cy-bz)2+(az-cx)2
b) (a2+b2)(x2+y2)-(ax+by+cz)2=(ax-by)2+(bx+ay)2
c) nếu (x-y)2+(y-z)2+(z-x)2=(y+z-2x)2+(z+x-2y)2+(x+y-2z)2 thì x=y=z
