I need some help understanding what exactly the derivative means in this problem:
The number of gallons of regular unleaded gasoline sold be a gas station at a price of dollars per gallon is given by .
What would mean? Would this value usually be positive or negative and why?
Well, I, at least, tend to drive less and would consider buying a car with better gas milage as the price of gas goes up! That means that the amount of gas bought or sold would tend to decrease as the price goes up and so the derivative would be negative.