Question

What is the sum of the arithmetic sequence 3, 9, 15..., if there are 26 terms?
A.) 2,028
B.) 1,452
C.) 2,268
D.) 1,728

Answer 1

1. find the 26th term
2. add the first 26 terms

Answer 2

What is the common difference?

Answer 3

To find the common difference, subtract a term from the next term.

Answer 4

d = common difference = 9 - 3 = 15 - 9
What is d?

Answer 5

the answer would be A

Answer 6

Formula to find the nth term:

\(\large a_n = a_1 + d(n - 1)\)

Formula to find the sum of the first n terms:

\(\large S_n = \dfrac{n(a_1 + a_n)}{2} \)

Using the formulas above, you get:

\(a_n = 153\)

\(S_n = 2028\)

Answer 7

You are correct.

Answer 8

okay thank you!(: