(1)依题得
?
1+d=q 1+5d=q2
,
d=3 q=4
∴an=3n-2,bn=4n-1;
(2)∵
=1
anan+1
=1 (3n?2)(3n+1)
(1 3
-1 3n?2
),1 3n+1
∴Sn=
[(1 3
-1 1
)+(1 4
-1 4
)+…+(1 7
-1 3n?2
)]1 3n+1
=
;n 3n+1
(3)假设存在常数a,b满足题意,把an=3n-2,bn=4n-1代入an=logabn+b,
得:3n-2=loga4n?1+b,
即(3-loga4)n+(loga4-b-2)=0对一切n∈N*都成立,
∴
,
3?loga4=0 loga4?b?2=0
解得:
.
a=
3
4
b=1
即存在常数a=
,b=1满足题设.
3
4