Simple and prints imaginary roots too!
float a,b,c,x1,x2,d,dsq;
printf("ax^2 + bx + c = 0");
printf("\nEnter a,b,c separated by commas : \n");
scanf("%f,%f,%f",&a,&b,&c);
d = b*b-(4*a*c);
if(d>=0)
{
dsq=sqrt(d);
x1 = (-b+dsq)/(2*a);
x2 = (-b-(dsq))/(2*a);
printf("\nRoot 1 : %f\nRoot 2 : %f",x1,x2);
}
if(d<0)
{
d = ((4*a*c)-pow(b,2))/(2*a);
printf("\nRoot 1 : %f+%fi",((-b)/(2*a)),d);
printf("\nRoot 2 : %f-%fi",((-b)/(2*a)),d);}