# Root locus region on real axis

Let the open loop transfer function of a positive feedback closed loop system be K(s−3)/(s^2+3s+2), where K is a non-negative real valued parameter. Consider the corresponding locus of closed loop poles. Which one of the following statements is TRUE? a)The region (-∞, -2) lies on the root locus b)The region (-∞, -1) lies on the root locus c) The region (-2, -1) lies on the root locus d) The region (-1, 3) lies on the root locus

I drew the root locus of the transfer function but there are two region on real axis (-infinity,-2) and (-1,3) . But only one option is correct. What option should I choose?

• You say, positive feedback. Most softwares and textbooks draw root locus for negative feedback. Are you sure the drawn locus is correct? – AJN Oct 27 '20 at 15:35
• Yes... It's positive feedback – Camila's voice Oct 27 '20 at 15:44

RootLocusPlot[k (s - 3)/(s^2 + 3 s + 2), {k, 0, 10}, FeedbackType -> "Positive"]