A problem I'm facing involves finding out the modulus of vectors. I now know how to solve and get the answer for 20. (a), but I am unsure how to do (b). I was thinking it would become |r-2r| = |-r| = |-5|. Is there any rule that would make it -|5| which would result in the answer being 5?
Also, I wanted to know how to solve for part (d) of the question. I know how to solve for (c) but did not understand how the vectors can be drawn for part (d).