An Apple Tree farmer

Question

A person is an apple tree farmer. She currently has 20 apple trees per acre, and each tree will yield an average of 200 apples. She is also told that for each additional apple tree she plants per acre, the average yield of each tree will decrease by 2 apples. How many additional trees should she plant per acre to maximize her harvest?

Answer 1

t represents the number of additional tree

A(t) = (20 + t)(200 - 2t)

Can you multiply out and determine maximum (vertex)?