Question

For the sequence given by an=4n+5 , answer the following:

a. Find the first five terms.

b. Find the sum of the first 25 terms.

c. Is this an arithmetic sequence? If so, how can you tell? If not, why not?

***please explain! Thank you!! :)

Answer 1

a.) First 5 terms are: 4(1) + 5, 4(2) + 5, 4(3) + 5, 4(4) + 5, 4(5) + 5 = 4 + 5, 8 + 5, 12 + 5, 16 + 5, 20 + 5 = 9, 13, 17, 21, 25

b.) 25th term = 4(25) + 5 = 100 + 5 = 105
sum of the first 25 terms = 25/2(9 + 105) = 25/2(114) = 285

c.) The sequence is an arithmetic sequence because, the sequence increases by addition of 4.