#include <math.h>
 
/* define your functions below */
 
double f1( double x)
{
  double y;
 
  y = x*(x*x - 2);
 
  return y;
}
 
double f2( double x)
{
  return x*x;
}
 
/* set f to list of function names with 0 at the end */
 
double (*f[])(double) = { f1, f2, 0};