Question

An online music store sells about 4000 songs each day when it charges $1 per song. For each $0.05 increase in price, about 80 fewer songs per day are sold. Use the verbal model and quadratic function to determine how much the store should charge per song to maximize daily revenue. R(x)=(1+0.05x)(4000-80x)

Answer 1

X is the number of $0.05 price increases 
so 
15 × 0.05 = $0.75 
and so, walla, (0.75, 4900) 
or 
increase price by $0.75 for max profit of $4900. 

otherwise your math was sound

Answer 2

Answer:

The best price is $1.75.

Step-by-step explanation:

Profit = Songs x Price  

Given equation is ;

$R(x)=(1+0.05x)(4000-80x)$

Solving this :

Let the number of $0.05 increases be x.

R(x) = $-4x^{2}+120x+4000$

The revenue is maximized when dR/dx = 0.  

dR/dx = $-8x+120$

The revenue is maximized when x = 15

Means when the price per song = $1.00 + ($0.05*15) = $1.75

Therefore, the best price is $1.75.