Answer:
x = 50
R = $2500
Step-by-step explanation:
Given in the question a quadratic equation,
−x² + 100x
To find the selling price, x, which will give highest revenue, y, we will find maximum value of parabola curve −x² + 100x
The value of -b/2a tells you the value x of the vertex of the function
−x² + 100x
here a = -1
    b = 100
Selling price = -(100)/2(-1)
          =  50
Â
R = −(50)² + 100(50)
 = 2500