Determine the reasonable domain

Question

A food packet is dropped from a helicopter and is modeled by the function f(x) = -15x²+ 6000. The graph below shows the height f(x), in feet, of the food packet at different times x, in seconds. 

 

The graph is a parabola where the x-intercepts are -20 and 20. The y-intercept is 6000 and the parabola is shaped like an upside down u. 

 

Use the graph to determine the reasonanle domain of f(x) based on the context. (This question is from my study guide for my final exam, can somebody please help me through it so I can be better prepared for my exam?) :-)

Answer 1

Hi Daysha,

 

Since x represents time, it can't be negative. This means that you are only interested in the right side of the parabola starting from the axis of symmetry.

The reasonable domain of f(x) is then x = [0, 20].

at x = 0 sec, the packet is dropped from the helicopter.

at x = 20 sec, the packet hits the ground.