Consider a unity negative feedback system with feed forward gain \(G\left( s \right) = \frac{K}{{s\left( {s + 1} \right)\left( {s + 2} \right)}}\)
The root-loci of the system cross the imaginary axis at:1
\(s = \pm j\sqrt 3 \)
2
s = ± j2
3
s = ± j3
4
\(s = \pm \;j\sqrt 2\)