Math grade 11

Question

Maximum or Minimum of a quadratic function revenue question
An electronic store sells an average of 60 entertainment systems per month at an average of $800 more than the cost price. For every $20 increase in the selling price, the store sells one fewer system. What amont over the cost price will maximize revenue?

Answer 1

r = (800 + 20x)(60 - x)

r = 2400 + 400x - 20x²

r = -20x + 400x + 2400    

 

maximum/minimum occurs at -b/2a.

For this situation, -400/(2)(-20), or 10.

 

What is the optimal price?