Quadratic function

Question

At a certain vineyard it is found that each grape vine produces about 10 lb of grapes in a season when about 500 vines are planted per acre. For each additional vine that is planted, the production of each vine decreases by about 1 percent. So the number of pounds of grapes produced per acre is modeled by

A(n) = (500 + n)(10 − 0.01n) 

where n is the number of additional vines planted. Find the number of vines that should be planted to maximize grape production.

Answer 1

Convert A(n) to a quadratic, i.e. vertex form and deteremine maximum.