#### Answer

(a) -2
(b) $-\frac{1}{2}$

#### Work Step by Step

(a) We calculate the net change between the two points given:
Net change = $f(5)-f(1)=2-4=-2$
(b) We calculate the average rate of change between $(1,4)$ and $(5,2)$:
Average rate of change = $\frac{2-4}{5-1}=\frac{-2}{4}=-\frac{1}{2}$