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

Jun 29, 2015

 =-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, $n = 17 , {a}_{1} = 8 , {a}_{n} = - 88$

$= \frac{17}{2} \left(8 - 88\right)$

$= \frac{17}{2} \times \left(- 80\right)$

 =-color(blue)(680