AnsI had this question
Step-by-step explanation:
Answer:
-52/7 or 7 3/7
-5 is also -35/7
2 3/7 is also 17/7
-35/7-17/7 = -52/7
-52/7 = 7 3/7
The formula of the sum of an arithmetic sequence:
We have:
substitute:
Answer: b. 21