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

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

mathstudent55 · Answer

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

mathstudent55 · Answer

What is the common difference?

mathstudent55 · Answer

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

mathstudent55 · Answer

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

ashy98 · Answer

the answer would be A

mathstudent55 · Answer

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:

$a_n = 153$

$S_n = 2028$

mathstudent55 · Answer

You are correct.

ashy98 · Answer

okay thank you!(: