哗啦1201
幼苗
共回答了18个问题采纳率:72.2% 举报
x+y分之xy=3,xy=3x+3y
xy+yz+zx分之xyz=2,xyz=2xy+2yz+2xz
3xz+3yz=2xy+2yz+2xz
z(x+y)=2xy
z=2xy/(x+y)=6(x+y)/(x+y)=6
1年前
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哗啦1201
因为x+y分之xy=3所以xy=3x+3y 因为xy+yz+zx分之xyz=2所以,xyz=2xy+2yz+2xz 所以3xz+3yz=2xy+2yz+2xz 整理得 z(x+y)=2xy 把xy=3x+3y代入上式得 z=2xy/(x+y)=6(x+y)/(x+y)=6