解:①显然an-a(n-1)=2∴d=2且a1=1∴an=2n-1②bn=1/(2n-1)(2n+1)∴∑bn=1/2*[1/1-1/3+1/3+````+1/(2n-1)-1/(2n+1)]=n/(2n+1) 如有疑问,可追问!