The rate of change is equivalent to the slope, so we draw a triangle against the linear plot
From the triangle drawn, y2 = 9, y1 =-3, x2=3, x1 =0
[tex]\text{Slope =}\frac{y_2-y_1}{x_2-x_1}[/tex][tex]=\frac{9-(-3)}{3-0}[/tex][tex]\begin{gathered} =\frac{9+3}{3} \\ =\frac{12}{3} \\ =4 \end{gathered}[/tex]The rate of change = 4
