实数a,b,c成等差数列,设公差为d；由于a,b,c不全相等,那么d≠0；有 a=b-d ,c=b+d ；1/a+1/c=1/(b-d)+1/(b+d)=2b/(b^2-d^2)而 1/b+1/b=2/b=2b/(b^2)由于d≠0,那么 (b^2)≠(b^2-d^2)即 2b/(b^2-d^2)≠2b/(b^2),那么1/a+...