#include<stdio.h>
#include<math.h>

int main()
{double a,b,c;
double x1,x2,disc,realpart,imagpart,root;
disc=b*b-4*a*c;
realpart=-b/(2*a);
imagpart=sqrt(-disc)/(2*a);

printf("There is a equation :a*x*x+b*x+c=0\n");
printf("please enter a,b,c:");
scanf("%lf,%lf,%lf",&a,&b,&c);

if(fabs(a)<1e-6)
{printf("it is not a 二次方程!");
root=-(b/c);
printf("the root is %f\n",root);
}

else    /* (a!=0) */
{
   if(fabs(disc)>1e-6)
   {  if(disc>1e-6)
   {printf("it is a 二次方程!");
 x1=(-b+sqrt(b*b-4*a*c))/(2*a);
 x2=(-b-sqrt(b*b-4*a*c))/(2*a);
 printf("there are two roots: x1=%f,x2=%f",x1,x2);}
      else
      {printf("it is a 根为虚数的二次方程! it has two complex roots: ");
 printf("x1=%8.4lf+%8.4lfi\n",realpart,imagpart);
 printf("x2=%8.4lf-%8.4lfi\n",realpart,imagpart);}
}
   else
{printf("it has two equal root:%8.4lf\n",-b/(2*a));}

}

return 0;
}