If x represents time, the average rate of change of the function f(x) in the first three seconds is

If x represents time, the average rate of change of the function f(x) in the first three seconds is -50.

The average rate of change of a linear function is the slope of the liner function. To find the slope of our linear function, we are using the slope formula:

where

is the slope of the line

are the coordinates of the first point on the line

are the coordinates of the second point

From our graph we can get the points (0, 150) and (3, 0), so , , , and . Let's replace the values in our formula to find the slope of our linear function:

Since the average of change a linear function is equal to its slope, the average rate of change of the function in the first three seconds is -50