@rcorless 

Is there any process to get like this

resultant(A, a01*(a20*b20 - a30*b10) + a11*a20*b11, a20*b20 - a30*b10)

I tried with 

B := a20*b20 - a30*b10;
               resultant(A, a11*a20*b11 + B*a01, B);

But not works 

@vv After simplifying A there will be terms involving  sigma+x, sigma*x & I want to put a and b in that places

@vv It is just a polynomial. No square roots. 

I want to get the coeff x*sigma^2, coeff x^2*sigma etc. How to do that?

@Carl Love Is it possible to get the Taylor series by letting sqrt(epsilon)=x about (x=0,lambda2=0)?

If yes please suggest the steps.

@Carl Love Thanks a lot

@Joe Riel Thanks for the information Joe. 

@Kitonum 

What is

``

Please give me a link from where I can read about it...

@acer Thanks a lot

@Carl Love Yes I need the 2nd presentation that you have mentioned but separeted by comma. Like

h1,   h2,    h3,

h4,   h5,    h6

AA1, AA2, AA3,

AA4, AA4, AA6

@Carl Love Yes I need two different rows.

@Carl Love Now it is exactly that I want. Thanks a lot.

@Carl Love Now it is exactly that I want. Thanks a lot.

@Carl Love Thanks for the reply. It works good but the only problem is that the entries of the list become sorted. I need then unsorted. How to convert tau so that I can get them unsorted( means for a specific value of h, I need corresponding value of tau and therefore there should have a one-one positional correspondence of h and tau.).

@Carl Love Thanks for the reply. It works good but the only problem is that the entries of the list become sorted. I need then unsorted. How to convert tau so that I can get them unsorted( means for a specific value of h, I need corresponding value of tau and therefore there should have a one-one positional correspondence of h and tau.).

The above code gives tau only. I am satisfied with this answer. Thank you very much for the answer.  But all values of tau are coming in a column. I want them in row format separeted by comma. for example 

-0.9785051795 + 0.7259062748 I, -1.071478821 + 0.6845304376 I, -1.131874061 + 0.6560618230 I,
  -1.175633397 + 0.6345196708 I, -1.207468201 + 0.6181877729 I,-1.229655595 + 0.6060305422 I

Please help me to get the answer.