#### Answer

a) $\textbf{v}(t) = <2, -4>$; Speed = $2\sqrt {5}$
b) $\textbf{a}(t) = <0, 0>$

#### Work Step by Step

$\textbf{r}(t) = <2 + 2t, 1-4t>$
$\textbf{v}(t) = \textbf{r}'(t) = <2, -4>$
Speed = $|\textbf{v}(t)| = \sqrt {(2)^2+(-4)^2} = 2\sqrt {5}$
$\textbf{a}(t) = \textbf{v}'(t) = <0, 0>$