A certain fast food restaurant wants to determine the increase in revenue per cheeseburger if sales are $45,000. Let the function [p=(120000-x)/(30000)] represent the price of x cheeseburgers.

Answer 1

p is price of x burger, then divide by x to get price per burger

Priceburger= 1/x * p
= 120000/30000x -1/30000
dPriceburger/dx= -4x^2
put in x=45000, and you have the increase in revenue per burger. assuming costs are the same (which they never are).