Characteristic Equation from Transfer Function

Correct Answer

B — (s + 1)²(s + 2) = 0

Concept and Reasoning

The poles of a closed-loop transfer function are the roots of its denominator. Therefore the characteristic equation is obtained by setting (s+1)²(s+2)=0.

Calculation / Key Relation

(s+1)²(s+2)=0

Exam Takeaway

Closed-loop characteristic equation = denominator = 0.

Common Mistake

Do not add numerator and denominator when the closed-loop transfer function is already given.