例4.9

#include<math.h>
int main()
{ double a,b,c,disc,x1,x2,realpart,imagpart;
scanf("%if,%if,%if",&a,&b,&c);
printf("The equation");
if(fabs(a)<=1e-6)
printf("is not a quadratic\n");
else
{disc=b*b-4*a*c;
if(fabs(disc)<=1e-6)
printf("has two equal roots:%8.4f\n",-b/(2*a));
else
if(disc>1e-6)
{x1=(-b+sqrt(disc))/(2*a);
x2=(-b+sqrt(disc))/(2*a);
printf("has distinct real roots:%8.4f and%8.4f\n",x1,x2);
}
else{realpart=-b/(2*a);
imagpart=sqrt(-disc)/(2*a);
printf("has complex rppts:\n");
printf("%8.4f+%8.4fi\n",realpart,imagpart);
printf("%8.4f-%8.4fi\n",realpart,imagpart);
  }
}
return 0;
}