bn=[(2n+1)(2n-1)]分之1 用裂项求和
问题描述:
bn=[(2n+1)(2n-1)]分之1 用裂项求和
答
bn=1/[(2n+1)(2n-1)]
=1/2[1/(2n-1)-1/(2n+1)]
Sn=1/2-1/(4n+2)