Answer
(a). $5$,
(b). $y=5x-2$
Work Step by Step
(a). From $x_1=-1$ to $x_2=1$, we have the average rate of change as $\frac{f(x_2)-f(x_1)}{x_2-x_1}=\frac{(5(3)-2)-(5(1)-2)}{3-1}=5$,
(b). The slope of the secant line is the same as the average rate of change in (a), $m=5$, use one point $(1,3))$, we can find the equation as $y-3=5(x-1)$ or $y=5x-2$
