What is the answer to this problem 3+4

Find the sum of the first 8 terms of the following sequence. round to the nearest hundredth if necessary.

[10 points, algebra 2]according to my answer key the restrictions are -1 and 4. but why not positive 1?

Atextile fiber manufacturer is investigating a new drapery yarn, which the company claims has a mean thread elongation of 12 kilograms with a standard deviation of 0.5 kilograms. the company wishes to test the hypothesis upper h subscript 0 baseline colon mu equals 12 against upper h subscript 1 baseline colon mu less-than 12 using a random sample of n equals 4 specimens. calculate the p-value if the observed statistic is x overbar equals 11.8. round your final answer to five decimal places (e.g. 98.76543).