In an arithmetic sequence, a17 = -40 anda28 = -73. Explain how to use this information to write a recursive formula for this sequence.

Answer:

The difference between the given terms is –73 – (–40) = –33. The difference between the term numbers is 28 – 17 = 11. Dividing –33 / 11 = –3. The common difference is –3. The recursive formula is the previous term minus 3, or an = an – 1 - 3 where a17 = -40.