Cell phone companies estimate that the total number of text messages (t) since the beginning of the month can be modeled by t=40×sqrt(x) where (x) is the number of days passed in the month. how many text messages were sent between the ninth and sixteenth day of the month?

The desired number is the difference between the number of messages sent by the 16th day and the number sent by the 9th day:

... n = t(16) - t(9)

... n = (40×√16) - (40×√9)

... n = 40×(4 - 3) = 40

40 text messages were sent between the ninth and sixteenth day of the month.

-4, -2, 1, 4

step-by-step explanation:

domain = x values

range = y values