What do the components of the vector equation mean?

Question

for example: (x,y)= (x1,y1) + t(x2,y2)

i don't know which one represents which, only that one of them is velocity, but i don't know which ordered pair is each

PLEASE HELP

Answer 1

(x,y)= (x1,y1) + t(x2,y2)
current pos = old position + time * velocity

Answer 2

(x,y) = (x1,y1) + t(x2,y2)

Think of (x1,y1) and (x2,y2) as being two vectors from the orgin to the two points. And t is a scalar ranging over the real numbers.

You can reach any point (x,y) on the line by adding the first vector to a multiple of the second vector. You get a multiple of the second vector by multiplying it by the scalar t.