Answer:
The sum of all the terms is -775.
Step-by-step explanation:
This appears to be an arithmetic sequence, with a common difference of 4.
The problem is, we don't know how many terms there are!
To find this, use the following formula:
last number = first number + (n - 1) * difference
In this case:
35 = -85 + (n - 1) * 4
35 = -85 + 4n - 4
4n = 124
n = 31
This means there are 31 terms in this sequence.
Now, for the sum. Use the following formula:
n(first number + last number), take this product and divide it by 2.
In this case:
31(-85 + 35) = -1550 / 2 = -775
