A certain fast food restaurant wants to determine the increase in revenue per cheeseburger if sales are $45000 . Let the function p=120000-x/30000 represent the price for x cheeseburgers.

Answer 1

revenue is quantity * price, so
r(x) = x*p(x) = 120000x - x^2/30000
r'(x) = 120,000 - x^2/15,000
so ∆r ≈ r'(x) * ∆x
so find x when r(x) = 45,000 and then use ∆x = 1