Chapter 14 - Calculus of Vector-Valued Functions - 14.2 Calculus of Vector-Valued Functions - Exercises - Page 720: 32

$$ L(t)= \langle-16,-20,-36 \rangle +t \langle4,5,9 \rangle .$$

Since $ r (t)=\langle4t,5t,9t \rangle, $ then we have the derivative vector $ r' (t)=\langle4,5,9 \rangle $ Then, the parametrization of the tangent line at $ t=-4$ is given by $$ L(t)=r (-4)+tr'(-4)=\langle-16,-20,-36 \rangle +t \langle4,5,9 \rangle .$$