The average rate of change of a function f(x) from x1 to x2 is given by:
[tex]\frac{f(x_2)-f(x_1)}{x_2-x_1}[/tex]
In this case we need the first three seconds so x1=0 and x2=3.
Calculate the values of the function at x=0 and x=3 to get:
f(0)=150 and f(3)=0.
Substitute these values into the formula for average rate of change:
[tex]\begin{gathered} \frac{f(3)-f(0)}{3-0} \\ =\frac{0-150}{3} \\ =\frac{-150}{3} \\ =-50 \end{gathered}[/tex]
Hence the avearage rate of change of the function for the first three seconds is -50.
Note that the negative sign shows that the function is decreasing in the time interval (first three seconds).
