P = (1, 4)
O = Intersect(xAxis, yAxis)
Q = (6, 2)
OP = Vector(O, P)
d = Vector(O, Q - P)
T4: "(x,y) =" + P + "+" + "t " + d
a = Line(P, Q)
T1: "d = PQ = " + Q + "-" + P + " = " + d