It's very simple in octave, just by entering the coefficients of the equation into the roots function

octave:1> roots([1,0,-1])

ans =



  -1

   1

See the online help

octave:2> help roots

 'roots' is a function from the file /usr/share/octave/3.8.1/m/polynomial/roots.m



 -- Function File: roots (V)



     For a vector V with N components, return the roots of the

     polynomial



          v(1) * z^(N-1) + ... + v(N-1) * z + v(N)



     As an example, the following code finds the roots of the quadratic

     polynomial



          p(x) = x^2 - 5.



          c = [1, 0, -5];

          roots (c)

          =>  2.2361

          => -2.2361



     Note that the true result is +/- sqrt(5) which is roughly +/-

     2.2361.



     See also: poly, compan, fzero.