Use the revenue and cost functions below to answer part A B
     Use the revenue and cost functions below, to answer part (A), (B), and (C).  R(x) = 75x - 3x^2 1 lessthanorequalto x lessthanorequalto 20  C(x) = 120 + 16x 1 lessthanorequalto x lessthanorequalto 20  (A) What is the profit function?  P(x) =  What is the domain of the profit function?  A. [1, 20]  B. [0, 20]  C. [0, 160]  D. [0, 75]  (B) Complete the table.  Click to select your answer(s).  (C) Choose the best graph of the profit function using the points from the table.   
  
  Solution
Given
Revenue Function R(x) = 75x - 3x2
Cost function C(x) = 120 + 16x
Profit Function P(x) = Revenue - Cost
= 75x - 3x2 - (120 + 16x)
= 75x - 3x2 - 120 - 16x // minus sign gets distributed over the bracket
= 59x - 3x2 - 120
C)
P(x) = 59x - 3x2 - 120
This represents a parabola.
The coefficient of x2 is negative therefore it will be a downward parabola.
Ans is option (D)

