求一元二次方程的实根或虚根

/*   求方程的根 */
#include"stdio.h"
#include "math.h"
main( )
{   float a, b, c, d, x1, x2, q,m,n;
printf("Please input a, b, c\n");
scanf("%f %f %f", &a, &b, &c);
d=b*b-4*a*c;
if(d>=0)
{  q=sqrt (d);       /*求实根*/
x1=(-b+q)/(2*a);
x2=(-b-q)/(2*a);
printf("d=%.2f,x1=%.2f, x2=%.2f \n ",d, x1, x2);
}
else
{ m=-b/(2*a);     /*求实部*/
n= sqrt(-d)/(2*a);      /*求虚部*/
printf("d=%.2f,x1=%.2f+%.2fi",d,m,n);
printf(", x2=%.2f-%.2fi",m,n);
}
}