(1)
2tSn-(2t+1)S(n-1)=2t (1)
2tS(n-1)-(2t+1)S(n-2)=2t (2)
(1)-(2)
2tan-(2t+1)a(n-1) = 0
an/a(n-1) = (2t+1)/2t
=>{an}为等比数列
(2)
(1)
2tSn-(2t+1)S(n-1)=2t (1)
2tS(n-1)-(2t+1)S(n-2)=2t (2)
(1)-(2)
2tan-(2t+1)a(n-1) = 0
an/a(n-1) = (2t+1)/2t
=>{an}为等比数列
(2)