3 points on the same line has a term called 'Collinear'. Are you at a loss of how to go about explaining why ABC is a straight line, why ABC is on the same line, why ABC is collinear?
They all meant the same thing. Here's the template you can use everything you need to explain why ABC is a straight line in a vectors question:
To have a better understanding, it is best that you know that what's the significance of scalar multiplication of vectors, I know it's like 'eeeeeeek' but what it really means is as followed: (Not as bad as you thought)
Note there's a bonus question at the end of the video. Try it and leave me your answer on the comments section.