Question

The characteristic equation of the control system is s^5+15s^4+85s^3+225s^2+274s+120=0 . What are the number of roots of the equation which lie to the left of the line s+1 = 0?

(a) 2

(b) 3

(c) 4

(d) 5

I had been asked this question during an internship interview.

Origin of the question is Compensation Techniques topic in division Digital Control Systems of Control Systems

Answer 1

The correct option is (c) 4

To explain: The solution is obtained with the help of the Routh-Hurwitz table and in this the solution is obtained by equating the value as s-1 in the given equation.