2、70

4, can't see clearly

6、9/4 Sn =(7/8 q- 14)/( 1-q)= 77/8

7.an=Sn-Sn- 1=2 to the power of (n- 1), geometric series.

The odd term is you 1 2 2 4 2 6...2 (2n-2).

The sum of the first n terms of odd terms is the 2n power of 2 minus 1 divided by 3.

8、(3^9-3^3)/2 =9828