Question: determine whether the points lie on straight lines

- A(2,4,2), B(3,7,-2), C(1,3,3)
- D(0,-5,5), E(1,-2,4), F(3,4,2)

Answer: first one no, second one yes

My work: only the one of the variables would be changing and it would be by a constant factor (e.g. 3,6,9,12...). I think this because a line has a constant slope.

Is it possible to plot 3d graphs by hand? If yes, how?