Afood packet is dropped from a helicopter and is modeled by the function f(x) = -12x2 + 19200. the graph below shows the height f(x), in feet, of the food packet at different times x, in seconds:
use the graph to determine the reasonable domain of f(x) based on the context.
all real numbers
x ≤ 19200
-40 ≤ x ≤ 40
0 ≤ x ≤ 40

 For this case we have the following function:
 
 When the food package is on the plane, we have that the height of the package is given by:
 
 Rewriting we have:
 
 When, time passes, the height decreases.
 When the time is 40 seconds (x = 40) the package reaches the ground and the height is 0.
 Therefore, a reasonable domain for the function is:
0 ≤ x ≤ 40

0 ≤ x ≤ 40