xy/(x+y)=1.
取倒數(shù)
(x+y)/xy=1
1/x+1/y=1.1
yz/(y+z)=2.
取倒數(shù)
(y+z)/yz=2
1/y+1/z=1/2.2
zx/(z+x)=3
取倒數(shù)
(z+x)/zx=3
1/z+1/x=1/3.3
1式+2式+3式得
2(1/x+1/y+1/z)=11/6
1/x+1/y+1/z=11/12.4
將2式代入4式得
1/2+1/x=11/12
1/x=5/12
x=12/5