a(n+1)=an/(an+1)1/a(n+1)=(an+1)/(an)=1+1/(an)1/a(n+1)-1/(an)=1所以1/(an)是以1为首项，公差为1的等差数列1/(an)=a1+(n-1)d=1+(n-1)=nan=1/n
