inter Algebra
posted by linda .
A band can sell 80 CDs at concert if they sell the Cds for $12 each. For every $1 increase in the price, they will sell 5 fewer Cds. Determine the price for a CD that will maximize the band's revenue.

Let x be the price.
The number sold is
N = 80  5(x 12)= 140 5x.
The revenue is 140x 5x^2 dollars.
Try completing the square, since you probably don't know how to use differential calculus yet. Maximum revenue ($980) is at a price where
140  10x = 0
x = $14
At a price of $13 or $15, the revenue is $975. 
is $14 by completing the square