## Calculus (3rd Edition)

(c) $r_3(t) = \langle 8-4t^3, 2+5t^2, 9t^3 \rangle$
$r_3(t)$ does not parametrize a line because the components do not have the same degree (the y-component has the the parameter $t$ raised to the second power while the x- and z- components have the parameter $t$ raised to the third power). The equations in (a) and (b) have the parameter $t$ raised to the first and third powers, respectively, in all three components.