Question: Depressed quartic equation solution

I have a depressed quartic equation with the quadratic term also removed. It has at least one positive real root which is the solution that I am looking for. There are three cases to consider. Two of the cases have trivial solutions. Maple gives its usual RootOf solution for the general case. My worksheet is below.

> restart;
> assume(b > 0, g > 0);
Depressed quartic equation with quadratic term also removed.
It has at least one real posivtive root -- the desired root.
> Eq1 := v^4-b*v-g = 0;
                               4             
                              v  - b v - g = 0
Case 1: b = 0, g > 0
> Eq2 := subs(b = 0, Eq1);
                                  4       
                                 v  - g = 0
> Sol2 := solve(Eq2, v);
                     (1/4)     (1/4)    (1/4)      (1/4)
                    g     ,  I g     ,   -g     ,   -I g    
> v = Sol2[1];
                                      (1/4)
                                 v = g    
Case 2: g = 0, b > 0
> Eq3 := subs(g = 0, Eq1);
                                 4         
                                v  - b v = 0
> Sol3 := solve(Eq3, v);
       (1/3)     1  (1/3)    1    (1/2)  (1/3)    1  (1/3)   1    (1/2)  (1/3)
  0,  b     ,  - - b         + - I 3      b     ,     - - b         - - I 3      b    
                    2               2                          2              2               
> v = Sol3[2];
                                      (1/3)
                                 v = b    
Case 3: g > 0, b > 0
> Sol1 := solve(Eq1, v);
                                        /   4                 \
                           RootOf\_Z  - b _Z - g/
 

I have been playing with the analytical solution to the quartic equation, but I get a royal mess. It seems to me that I should be able to get a "reasonably simple" expression for the positive real root of the simple quartic defined in Eq1 with the given assumptions on b and g, but I don't know enough about the theory of polynomial roots. I am also surprised that Maple doesn't know the analytic solution to the quartic equation.

Maybe I'm being overly optimistic, but will appreciate any help with this problem. Thanks.

Neill S.

Please Wait...