compute eigen values of a matrix with symbolic variable

%The code is :

syms A ;

matrix = [A, (2*A)-1; 4*A, 2*A];

A = 1.0;

matrix

subs(matrix, A,1)

A

% reset(symengine)

matrix

eig(matrix)

I want to compute the eigen values of a matrix filled with symbolic variable A. I used

1. reset(symengine) option 
2. subs(matrix, A,1)

but i am getting the answer with symbolic variable only as follows:

(3*A)/2 - (33*A^2 - 16*A)^(1/2)/2
(3*A)/2 + (33*A^2 - 16*A)^(1/2)/2

But i want the answer(eigen values of matrix ) as

matrix=[1 1;4 2];
eig(matrix)

-0.5616
 3.5616

Please help in this regard.

Answer 1

[Walter Roberson]

subs(matrix, A, 1) does not change matrix: it produces a new value with the substitution made.

eig(double(subs(matrix, A,1)))

[Thayumanavan]

For this code i got Error in MuPAD command: DOUBLE cannot convert the input expression into a double array. but i changed double to vpa i got the answer .

eig(vpa(subs(matrix, A,1))) (or) eig(eval(matrix)). Thank you