Which summation formula represents the series below? 13 + 9 + 5 + 1

Step-by-step explanation:

The given expression is

The terms of this series are

13,9,5,1

It is an AP. Here, first term is 13 and common ratio is -4.

The nth term of an AP is

where, a is first term and d is common difference.

The nth term of given AP is

The summation formula of an AP is

The value of n is 4 because the number of term is 4. So, the summation formula is

lolololkzaxio2ier286udeg