נוסחת השורשים

#include <stdio.h>
#include <math.h>
double f(double a,double b,double c,double *p1,double *p2)
{
    double m;
    if(a==0 || (b*b-4*a*c)<0)
        return 0;
    if((b*b-4*a*c)==0)
    {
        *p1=(-b)/2.0*a;
        return 1;
    }
    m=sqrt(b*b-4*a*c);
    *p1=((-b)+m)/(2.0*a);
    *p2=((-b)-m)/(2.0*a);
    return 2;
}
void main()
{
    double a,b,c,k;
    double x1,x2;
    printf("Enter a , b , c:  ");
    scanf("%lf%lf%lf",&a,&b,&c);
    k=f(a,b,c,&x1,&x2);
    if(k==0)  printf("No Solution\n");
    if(k==1)  printf("x1: %.2lf\n",x1);
    if(k==2)  printf("x1: %.2lf    x2: %.2lf\n",x1,x2);
}