/* --------------------------------- */
/* save as fb.h                      */
/* --------------------------------- */
double f(
double x,
double y)
{
 return(     (x*x*x * y*y  - 2*x*x  * y + 3*x) );
}
char  feq[] = "x**3 * y**2 - 2*x**2 * y + 3*x";
/* --------------------------------- */
double f_x(
double x,
double y)
{
 return(       (3*x*x   * y*y  - 4*x * y + 3) );
}
char Dfeq_x[] = "3*x**2 * y**2 - 4*x * y + 3";
/* --------------------------------- */
double f_y(
double x,
double y)
{
 return(       (2*x*x*x * y - 2*x*x)  );
}
char Dfeq_y[] = "2*x**3 * y - 2*x**2";
/* --------------------------------- */
double f_xx(
double x,
double y)
{
 return(        (6*x * y*y  - 4*y) );
}
char Dfeq_xx[] = "6*x * y**2 - 4*y";
/* --------------------------------- */
double f_yy(
double x,
double y)
{
 return(       (2*x*x*x)  );
}
char Dfeq_yy[] = "2*x**3";
/* --------------------------------- */