Have a question which is as above for line through points (0, 1/2, 1) and (2,1, -3)

They way I understand it this is what you do. Get a directional vector between the two points ie let (0, 1/2, 1) be point A and (2, 1, -3) be point B. Thus vector AtoB is < (2-0), (1-1/2), (-3-1)> giving < 2, 1/2, -4>

Now parametrics would be x= (0+2t) , y=( 1/2+1/2t) and z = (1+ (-4t))

giving symetric as being x/2 = (2y-1) = (z-1)/-4

But it looks like I'm wrong can someone please advise what I am doing wrong here.