Intro to Control - 12.4 Root Locus Basics Part 2

Part 2 of explaining how to draw the root locus for a (negative) feedback control system. Showing that the root locus must be symmetric about the real axis and that it also exist on the real axis to the left of an odd number of the open-loop poles or zeros.
Correction: The forth rule about the real axis should be: "The real axis root locus exists to the left of an odd number of poles or zeros of G(s)H(s)." Sorry for the confusion!