Unable to compute roots for polynomial equation

This code creates an "n"th degree polynomial equation for an "n" degree pendulum and I'm unable to complete the last step which is to solve the polynomial roots. As a check, I'm comparing it to the attached example (see below code). I need to keep it generic (not specific to n=3).

The roots come up as long strings of equations with a mysterious "i" term. (See outputs below). How do I fix this?

n=3
syms m g l x w0
g=1;
l=1;
m=1;
w0=sqrt(g/l);

    T=zeros(n);
       for i=1:n;
           T(i,:)=n+1-i;
           T(:,i)=n+1-i;
       end
  T=T;

V=eye(n);
  for i=1:n;
     V(i,i)=n+1-i;
  end
V=V;

A=(eye(n)*(-w0^2)+ ones(n)*(x*w0^2));  %Set Up for w^2*T-V  
A=A.*T                              ;  %A=[w^2*T-V]/[ml^2]
B=det(A)                            ;  
C=B/w0^(2*n)                        ;  %EQN 10.122 IN ATTACHED EXAMPLE

D=coeffs(C)
D=fliplr(D)
roots(D)                            ; %THESE SHOULD MATCH THE COEFFICIENTS IN EQN 10.123 IN ATTACHED IMAGE

The outputs are as follows. Everything looks great until the very last step- finding the roots.

C =

x^3 - 9*x^2 + 18*x - 6

D =

[ -6, 18, -9, 1] [ 1, -9, 18,-6]

ans =

                                                                              3/(3 + 18^(1/2)*1i)^(1/3) + (3 + 18^(1/2)*1i)^(1/3) + 3
 3 - (3 + 18^(1/2)*1i)^(1/3)/2 - (3^(1/2)*(3/(3 + 18^(1/2)*1i)^(1/3) - (3 + 18^(1/2)*1i)^(1/3))*1i)/2 - 3/(2*(3 + 18^(1/2)*1i)^(1/3))
 3 - (3 + 18^(1/2)*1i)^(1/3)/2 + (3^(1/2)*(3/(3 + 18^(1/2)*1i)^(1/3) - (3 + 18^(1/2)*1i)^(1/3))*1i)/2 - 3/(2*(3 + 18^(1/2)*1i)^(1/3))

Answer 1

[Torsten]

Use

r=roots(D);
disp(eval(r));

Best wishes

Torsten.

[Stephen Figueira]

This seems to partially fix the problem, except the output is not sorted correctly (it's easy to discern when n=3, but when n=50+ it becomes difficult). I've tried sort commands but the non-real terms throw it off.

D =

[ 1, -9, 18, -6]

     6.2899 - 0.0000i
     0.4158 - 0.0000i
     2.2943 + 0.0000i