Question

If Second term of a Geometric progression is. 2 and 10th term is 1 what is First term ? what is 128 nth term ?​

Answer 1

Answer:

If you know this following infinite series , the answer becomes relatively easy,

1 + 1/2 + 1/4 + 1/ 8 + ……. = 2

This is a convergent series where each of the term is a term of geometric progression where the first term is 1 and the common ratio is 2.

Now , multiply the series by 4 to get the sum 8 . 4( 1 + 1/2 + 1/4 + …) = 4 (2)

Or , 4 + 2 + 1 + 1/2+ ….= 8

Therefore, the first term is 4.