Could you please help with this question

What is the quadric regression equation that fits these data

At a sale this week, a desk is being sold for $213. this is a 29% discount from the original price. what is the original price?

The john deere company has found that revenue,in dollars, from sales of heavy-duty tractors is a function of the unit price p, in dollars, that it charges. if therevenue r is r(p)= -1/2p^2 +1900pa)how much revenue will the company generate if they sell 700 tractors? b) how many tractors does the company want to sell to maximize the revenue?