Problem Set

Quadratic Function



1. The publisher of an medical newsletter estimates that with x thousand subscribers its monthly revenue and cost (in thousands of dollars) are given by the following:


            R(X)  = 32x - .21x2


            C(x)  =  195  + 12x


Determine the number of subscribers needed for the publisher to break-even.




Profit equals revenue less cost. The breakeven point occurs where profit is zero or when  revenue equals cost.


            Profit = R(x)  - C(x)




            set profit  = 0




Solve using the quadratic formula where a = 195, b = 20, and c = .21.








Breakeven points occur where the publisher  has either 12,000 or 84,000 subscribers. Between these two points the publisher will be profitable.