function f = p20_f ( x )

%*****************************************************************************80
%
%% p20_f() evaluates the objective function for test 20.
%
%  Licensing:
%
%    This code is distributed under the MIT license.
%
%  Modified:
%
%    23 February 2026
%
%  Author:
%
%    John Burkardt
%
%  Input:
%
%    real x: the argument.
%
%  Output:
%
%    real f: the function value.
%
  f = x.^3 - 3.0 * x.^2 - 5.0 * x + 8.0;

  return
end
