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X+Y+Z=7,X2+Y2+Z2=11,XYZ=6则1/X+1/Y+1/Z=
人气:240 ℃ 时间:2020-03-24 20:01:11
解答
因为(x+y+z)²
=x²+y²+z²+2xy+2yz+2xz
所以 2xy+2yz+2xz
=(x+y+z)²-(x²+y²+z²)
=49-11
=38
可得:xy+yz+xz=19
所以1/x+1/y+/z
=(yz+xz+xy)/xyz
=19/6
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