L
lequan19942011


giải hệ
[TEX]\left\{x^2+y^2+z^2+2xy-xz-yz=3\\ x^2+y^2+yz-xz-2xy=-1[/TEX]

[TEX]\left\{x^2+y^2+z^2+2xy-xz-yz=3\\ x^2+y^2+yz-xz-2xy=-1[/TEX]
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