we need to find the maximum revenue after increasing the price?

Question

a concert is selling tickets. Their last concert sold 1000 tickets for $20 each. Market research suggests that for every $1 increase in price, 90 fewer people would come. By how much should they increase ticket prices to maximize revenue?

Answer 1

x represents the number of increases

 

r = (1000 - 90x)(20 + x) 

 

Convert in to vertex form and answer?