# Electronics and Communication Engineering - Automatic Control Systems - Discussion

16.

First column elements of Routh's tabulation are 3, 5, , 2. It means that there

 [A]. is one root in left half s plane [B]. are two roots in left half s plane [C]. are two roots in right half s plane [D]. is one root in right half s plane

Explanation:

Since there are two sign changes in the first column, hence two roots in right half plane.

 Kishore said: (Nov 23, 2014) If there is negative sign in Routh's tabulation system became unstable. It means roots are at right half of s-plane. But here only one negative sign how two roots in right half s-plane?

 Ta Meself said: (Feb 8, 2016) You have to look at sign CHANGES!

 Swati said: (Jul 24, 2016) As root +5 changes to -3/4, here one sign change takes place and again from -3/4 to +1/2 second sign change occurs so there are two roots in the right half of s-plane.

 Ajay said: (Jul 29, 2016) Well explained @Swati.

 Shivani Aggarwal said: (Oct 27, 2016) Right, you are correct @@Swati.

 Pkn said: (Dec 19, 2017) Correct @Swati.

 Manjunath said: (Jan 16, 2018) Well explained @Swati.

 Mukish Kumar said: (Nov 15, 2018) Great, very clear explanation. Thanks @Swati.