Question

What is the sum of a 17–term arithmetic sequence where the first term is 8 and the last term is –88?

Answer 1

`=-color(blue)(680`

Explanation:

The formula for sum of an Arithmetic Sequence when the first term `a_1`, number of terms `n` and last term `a_n` are given is:

`color(blue)(Sum = (n/2)(a_1+a_n)`

Here, `n=17, a_1 = 8 , a_n=-88`

`= 17/2 (8- 88)`

`= 17/2xx (-80)`

`=-color(blue)(680`