>                 /             /         2          \\    
>              1  | 2    2      |/ 2    2\       2  2||    
>       eqn := - +\b  + a , sqrt\\b  + a /  - 4 a  c // - c
>              2                                           
                                                     (1/2)    
        1  2   1  2   1 / 4      2  2    4      2  2\         
 eqn := - b  + - a  + - \b  + 2 b  a  + a  - 4 a  c /      - c
        2      2      2                                       
>                          solve(eqn, c)
                               2    2