ab/(a+b)=1/2,bc/(b+c)=1/3,ac/(a+c)=1/4
(a+b)/ab=2,(b+c)/bc=3,(a+c)/ac=4
1/a+1/b=2,1/b+1/c=3,1/a+1/c=4
(1/a+1/b+1/c)=(2+3+4)/2=9/2
1/a=(1/a+1/b+1/c)-(1/b+1/c)=9/2-3=3/2
1/b=(1/a+1/b+1/c)-(1/a+1/c)=9/2-4=1/2
1/c=(1/a+1/b+1/c)-(1/a+1/b)=9/2-2=5/2
所以,
a=2/3,b=2,c=5/2