Write the series using summation notation
-2+1+6+13+22+...

Step-by-step explanation:

Series in Summation Notation

We must try to find a general formula for each term and then use summation to generalize the sum of all the terms for any value of n, the term number.

The series is

The difference between consecutive terms will be computed:

We can see that

Applying summation on both sides:

Knowing that

Similarly, the sum of the left side is found to be

Replacing into the above equation, we find

Solving

Having the general term, the series is expressed as

For n=0 to infinity

i got 10.28 but that rounds up to 10.3

to determine the unit cost your would divide the total cost by the number sold.

7 bagels for $4.41       $4.41/7 = $.63 each at fresh side

5 bagels for $3.60         $3.60/5 = $.72 each at value mart