A cell phone manufacturer predicts pre-orders of their new cell phone using the function: P(d)=-2\sqrt(-d)+20

Question

P=pre-orders(in millions) of the phone
d=days before the release date
*if you search the graph up on desmos or a graphing site you will see the y coord. goes up to 20.
a) Indicate what the domain and range are meant for in this context. What do they show/explain?
b)Determine the number of pre-orders that the company can expect, 40 days before the release date of the cell phone.

Answer 1

It appears you have intended that
p(d) = -2/√(-d) + 20
(a) since √x is undefined for x<0, I assume d is really the number of days after release, so that -d is positive before the release. The range means that pre-orders go down as the release date gets near.
(b) p(-40) = 20-2/√40 = 19.68

Answer 2

Thank you for making sense out of that oobleck.

Answer 3

Apologies I couldn't figure out how to create the square root sign on my pc. Thank you for the understanding of the range.