Question

The polynomial s^4+Ks^3+s^2+s+1=0 the range of K for stability is _____________

(a) K>5

(b) -10<K

(c) K>-4

(d) K-1>0

This question was posed to me in unit test.

Query is from Relative Stability Analysis topic in division Stability and Algebraic Criteria of Control Systems

Answer 1

Right option is (d) K-1>0

For explanation I would say: Solving using Routh array we get K-1>0 and is always negative for K>1.