Answer:
-50
Explanation:
The average rate of change is synonymous with the slope. Therefore, we will find the slope of the function from x=0 to x=3.
So, we will use the endpoints of the function.
At x=0, f(x)=150. Thus, we have the point (0, 150).
At x=3, f(x)=0. Thus, we have the point (3, 0).
Now, we can use the slope formula:

Let (0, 150) be (x₁, y₁) and let (3, 0) be (x₂, y₂). Substitute:

Therefore, the average rate of change for the first three seconds is -50.