I am trying to figure out the one highlighted in red in page 3.

To make the system stable , it requires extra terms (which is the one highlighted in red). However , how do I determine this value? I have no idea how the one highlighted in red is derived . Could anyone help with this ?

Do note that this is not a homework question. This is taken from a lecture note.

 

Hi,

What control methods did you learn so far in the past?
For example, state variable feedback, root locus.