设 z/(x+y)=y/(x+z)=x/(y+z)=1/k,则:
z=1/k(x+y) (1)
y=1/k(x+z) (2)
x=1/k(y+z) (3)
(1)+(2)+(3)得：x+y+z=2*(1/k)(x+y+z),即1/k=1/2；
所以k=2z/(x+y)=y/(x+z)=x/(y+z)=kz/(x+y)=y/(x+z)=x/(y+z)=k如果是k的话，那么就是z=k(x+y) (1) y=k(x+z) (2) x=k(y+z) (3) (1)+(2)+(3)得：x+y+z=2*k(x+y+z),即k=1/2；