Chapter 12: Vectors and the Geometry of Space - Section 12.5 - Lines and Planes in Space - Exercises 12.5 - Page 726: 5

$x=0,y=2t, z=t$

As we know the parametric equations of a straight line for a vector $v=v_1i+v_2j+v_3k$ passing through a point $P(a,b,c)$ is given by $x=a+t v_1,y=b+t v_2; z=c+t v_3$ Since, we have $P(0,0,0)$ and $v=2j+k$ or, $v=\lt 0,2,1 \gt$ Our parametric equations are: $x=0,y=2t, z=t$