So with P(x) = -5x^2 + 550x - 5000 ...

... I'm going to sub in 55 into x to determine the maximum profit. (This is just based off of a question that I've been working on)

P(55) = -5(55)^2 + 550(55) - 5000

I've subbed in everything correctly now I just need to solve it. This is what I've come up with.

P(55) = -5(55)^2 + 550(55) - 5000

0= -5(55)^2 + 550(55) - 5000 - 55

0= -5(55)^2 + 550(55) - 4945

I'm not sure whether I'm doing it right.