clue needed on using results of previous computations



Rich--

Solve returns equations rather than expressions because sometimes it
does not get a fully explicit solution.  For example:

   solve(f(x)-3=2*f(x),x)

      =>

   [ f(x) = -3 ]

--------------

I think the way I would do your problem is as follows:

  expr: x*x + 5*g*x        /* No reason to define as an equation with y
*/

  dexpr: diff(expr1,x)     /* No reason to define a function f */

  sols: solve(dexpr1=0,x)

      =>
          [ x = -5*g/2 ]

  /* Verify that solutions are explicit by eye */

  vals: map(rhs,sols);     /* Preserves multiple solutions */

  plot2d(vals,[g,0,10])

or, more concisely:

  plot2d(map(rhs,solve(diff(EXPR,x),x)),[g,0,10])

if you're confident that the solutions will be explicit.

Of course, whether this makes sense in the general case depends on how
you want to generalize....

      -s