Question

已知ab/(a+b)=1/3,bc/(b+c)=1/4,ac/(a+c)=1/5,求代数式abc/(ab+bc+ac)的

Answer 1

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

1/a+1/b=3,1/b+1/c=4,1/c+1/a=5

1/a+1/b+1/c=(3+4+5)/2=6

abc/(ab+bc+ac)=1/(1/a+1/b+1/c)=1/6