An arithmetic sequence is represented as 5 , 9 , 13 , ... with the nth term represented as 4n + 1. Write a formula to represent the sum of the first n terms.

A)Sn = n^2 + 4n
B)Sn = 2n^2 + 3n
C)Sn = n^2 + 3n - 5
D)Sn = 2n^2 + 4n - 3

Question

An arithmetic sequence is represented as 5 , 9 , 13 , ... with the nth term represented as 4n + 1. Write a formula to represent the sum of the first n terms.

A)Sn = n^2 + 4n	
B)Sn = 2n^2 + 3n	
C)Sn = n^2 + 3n - 5	
D)Sn = 2n^2 + 4n - 3

anonymous · Answer

General formula is $$(n(a+l))/2$$

a = 5 it's the first term
l = 4n + 1 it's the last term
n = n number of terms

(n (5 + 4n + 1))/2

(n(4n+ 6))/2

2n^2+3n

B is the answer