Tracking Points

Age 14 to 16 Challenge Level:
Copies of the line segment AB that joins the points (0,0,0) to (1,1,1) are linked together (end-to-end) in a chain starting at (0,0,0). What would the coordinates of the ends of the tenth segment be? 

If a second line segment (CD) starts at (0,0,0) and ends at (1,3,2) and copies of this are made and joined end-to-end to it, what would the coordinates of the ends of the 2nd segment be? The tenth segment? The nth segment?

What if the chain of the line segment AB described in the first paragraph started at (1,0,-1)?
Where would the ends of the nth segment be this time?
Where would the ends of the nth segment be if the first segment started at (a,b,c)?

What if copies of the second line segment, CD, started at (-3,0,2) and were placed end to end. Where would the ends of the nth segment be?
If the chain started at (a,b,c) where would the ends of the nth segment be?

If you now make lots of copies of the two line segments and decide to place them end-to-end alternately, investigate the end points of the nth segment for different starting points.