故{an}的通项公式为an=4n-2,即{an}是a1=2,公差d=4的等差数列.
设{bn}的公比为q,则b1qd=b1,d=4,∴q=
1 |
4 |
故bn=b1qn-1=2×
1 |
4n-1 |
2 |
4n-1 |
(II)∵cn=
an |
bn |
4n-2 | ||
|
Tn=c1+c2+…+cn
Tn=1+3×41+5×42+…+(2n-1)4n-1
4Tn=1×4+3×42+5×43+…+(2n-3)4n-1+(2n-1)4n
两式相减得,3Tn=-1-2(41+42+43+…+4n-1)+(2n-1)4n=
1 |
3 |
∴Tn=
1 |
9 |