Question

Find the sum of a finite arithmetic sequence from n = 1 to n = 10, using the expression 3n − 8.

Answer 1

The answer is 85

Explanation:

The equation used to find the sum of an arithmetic series is: (n/2) * (a1 + an).

n in this case is 10 (the number of numbers in the series)

an is 22 (plug in 10 to the expression 3n-8)

and a1 is -5 (plug in 1 to the expression 3n-8)

so when you plug everything in to the final equation, you get

(10/2) * (-5 + 22)

5 * 17

85