Question

What is the sum of the first eight terms of the series?

Answer 1

-625

Explanation:

We have a geometric series which follows `a_n =ar^(n-1)`

`a="first term"=-500`
`r="common ratio"=a_2/a_2=-100/-500=1/5`

Sum of a geometric series is given by:
`S_n=a_1((1-r^n)/(1-r))`

`S_8=-500((1-0.2^8)/(1-0.2))=-55(0.99999744/0.8)=-500(1.2499968)=-624.9984~~-625`