(1)
令n=1,得a1=-1.
Sn=2an+n,S(n+1)=2a(n+1)+n+1.
两式相减,得a(n+1)=2a(n+1)-2an+1.
整理得a(n+1)-1=2(an-1),a1-1=-2.
综上,数列{an-1}是首项为a1-1=-2,公比为2的等比数列.
(2)
an-1=(a1-1)×qⁿ⁻¹=-2ⁿ
∴an=1-2ⁿ,bn=1/(2ⁿ+1).
∵2ⁿ+1>2ⁿ
∴bn<1/2ⁿ
∴Tn=1/(2+1)+1/(4+1)+...+1/(2ⁿ+1)
<1/2+1/4+...+1/2ⁿ
=1-1/2ⁿ
<1
综上,得证.