Question

If the nth partial sum of the sequence an is given by

Answer 1

This is an example of a series in arithmetic progression.

The nth term an can be calculated using the formula:

an = a1 + (n – 1) d

where: a1 = is the 1st term of the series

d = common difference

Calculating for the 1st term:

a1 = 2k + 4 = 2 (1) + 4 = 6

Calculating for the common difference by :

d = a2 – a1

d = 2 (2) + 4 – 6

d = 2

 

Therefore calculating for an:

an = 6 + (n – 1) 2

an = 6 + 2n -2

an = 2n + 4

Therefore the answer is B. 2n+4