find

Asked by  | 3rd Oct, 2008, 07:45: PM

Expert Answer:

20+2+22 +......+2r

This is a GP with a = a and r = 2

Sn  = a (rn  -1 )  /  r  -   1

= 1 ( 2n  - 1)  / 2-1    =  ( 2n  - 1)

Answered by  | 11th Oct, 2008, 09:54: PM

Queries asked on Sunday & after 7pm from Monday to Saturday will be answered after 12pm the next working day.