How do you find $a_1$ for the geometric series given $S_n=1530$ , r=2, n=8?

Question

2361 views around the world

You can reuse this answer
Creative Commons License

Answer 1 · 2016-12-11T16:15:11

$a_1=6$

In a Geometric series $n^(th)$ term of the series $S_n$ , where $|r|>1$ is given by $S_n=a_1(r^n-1)/(r-1)$ .

Here $S_n=1530$ , $r=2$ and $n=8$ and as such

$1530=(a_1×(2^8-1))/(2-1)$

= $(a_1×255)/(2-1)$

= $a_1×255$

Hence, $a_1=1530/255=6$ .

How do you find a_1a_1 for the geometric series given S_n=1530S_n=1530, r=2, n=8?