The first thing you should know is that you have two points in the space:
a (2, 0, -1)
b (2, 2, 3)
To form the ab vector we have:
ab = b - a = (2, 2, 3) - (2, 0, -1)
ab = (0, 2, 4)
Or equivalently:
ab = 0i + 2j + 4k
answer:
a vector with a representation given by the directed line segment ab is
ab = 0i + 2j + 4k
