Factor the polynomial completly. a. (x+1)(x+3)b. (x-1)(x-3)c. (x+3)(x-1)d. cannot be factoredplz asap

Suppose you are an avid reader and are looking to save money on the cost of books instead of paying about $20 for each book, you decide to look into purchasing a kindle for $120 you can purchase e-books for about $5 each 1. find the slope-intercept equation for the cost of the hard copy of books using x to represent the number of books 2. find the slope-intercept equation for the cost of the kindle with cost of e-books using x to represent the number of books