Solution for Problem 8.2.2

 Evaluate the sum.    

Add the first five terms of the sequence 
an
= n2 + 3n   from Your Turn  1.  

Solve

            Step

The first five terms are  
4, 10, 18, 28, 40
n = 1 means start at 1
5 means
end at 5.

=  4 + 10 + 18 + 28 + 40 = 100