A store has a sale on books. The price is $17.55 for one book, $16.70 each for 2 books, $15.85 each for 3 books, and $15 each for 4 books. If this pattern continues, how much per book will it cost to buy 7 books?
Cost for 7 books will be
The price per book forms an AP
The cost if 7 books are bought will be
Price difference with each additional book purchased is
The formula for price per books seems to be: