Question

How do you find `a_1` for the geometric series given `S_n=-364`, r=-3, n=6?

Answer 1

`a_1 = 2`

Explanation:

We use the formula `s_n = (a(1 - r^n))/(1 - r)` to find the sum of a geometric series.

`-364 = (a(1 - (-3)^6))/(1 - (-3))`

`-364 = (a(-728))/(4)`

`-364 = -182a`

`a = 2`

Hopefully this helps!