The formula for calculating the rate of change of a function is expressed as:
[tex]f^{\prime}(x)=\frac{f(b)-f(a)}{b-a}[/tex]Using the connecting points x = -8 and x = -5 on the graph, this means:
a = -8 = x1
b = -5 = x2
f(b) is f(-5) which is the corresponding y-values at x = -8
f(a) is f(-8) which is the corresponding x-values at x = -5
From the graph;
f(b) = f(-5) = -20 = y2
f(a) = f(-8) = -10 = y1
Determine the change in y and change in x
[tex]\begin{gathered} \triangle y=y_2-y_1=-20-(-10) \\ \triangle y=-20+10=-10 \\ \triangle x=x_2-x_1=-5-(-8) \\ \triangle x=-5+8=3 \end{gathered}[/tex]Find the average rate
[tex]\begin{gathered} Average\text{ rate of change}=\frac{f(b)-f(a)}{b-a}=\frac{\triangle y}{\triangle x} \\ Average\text{ rate of change}=-\frac{10}{3} \end{gathered}[/tex]For the grah , draw a line connecting the coordinate point (-5, -20) and (-8, -10)