Answer
(a). $4$,
(b). $y=4x-8$
Work Step by Step
(a). From $x_1=2$ to $x_2=4$, we have the average rate of change as $\frac{h(x_2)-h(x_1)}{x_2-x_1}=\frac{((4)^2-2(4))-((2)^2-2(2))}{4-2}=4$,
(b). The slope of the secant line is the same as the average rate of change in (a), $m=4$, use one point $(2,0)$, we can find the equation as $y=4(x-2)$ or $y=4x-8$
