Y=2x y is the amount of money made from the sold books x is the number of books that are sold (it is x because you don't know how many will be sold, so you have to account for all possibilities) 2x is because every book is sold for 2 dollars, so that mean x is multiplied by 2 to get y
I find it best to switch everything exponents when taking derivatives. F(x) = 7/x Same as.. F(x) = 7x^-1 Take derivative.. F'(x) = -7x^-2 Plug in x = 1 F'(1) = -7(1)^-2 F'(1) = -7
