Help! I don't know how to solve

Question

An electronics store is deciding how to price one of its products. The equation P = -25d 2 + 50d predicts the total profit P as a function of the product's price in dollars d. What price will produce the highest total profit? (where is the vertex?)

Answer 1

P(d) = -25d(d-2)
the vertex is midway between the roots, at d=1
or, using the vertex form,
P(d) = -25(d^2-2d+1) +25 = -25(d-1)^2 + 25

Answer 2

Thank you so much!