求方程的根，编译的时候发现不进if语句里

Question

求问各位大佬，不知道那一步出了错
#include <stdio.h>
#include <math.h>
int main()
{
double a,b,c,d,x1,x2;
printf("Input a,b,c=");
scanf("%f,%f,%f",&a,&b,&c);
d=bb-4ac;
if(d>0)
{
x1=(-b+sqrt(d))/(2a);
x2=(-b-sqrt(d))/(2a);
printf("The equation has distinct real roots:%f and %f\n",x1,x2);
}
if(d==0)
{
x1=x2=-b/(2a);
printf("The equation has two equal root:%f\n",x1);
}
if(d<0)
{
printf("The equation have no real roots.\n");
}
return 0;
}

Answer 1

scanf("%lf,%lf,%lf",&a,&b,&c);