C语言编写的求一元二次方程的根（实根和复根）

//2010.11.17一元二次方程的根
#include<stdio.h>
#include<math.h>
main(){
float a,b,c,x1,x2,derta;
printf("aX^2+bX+c=0  please input the number a  b  c:\n");
scanf("%f %f %f",&a,&b,&c);
if(a!=0){
derta=b*b-4*a*c;
if(derta>0){
           x1=(-b+sqrt(derta))/(2*a);
   x2=(-b-sqrt(derta))/(2*a);
   printf("two different real roots\n");
   printf("x1=%2f,x2=%2f\n",x1,x2);
}
else
{  
if(derta==0){
     x1=-b/2*a;
   printf("one real root\n");
   printf("x1=%2f\n",x1);
}
else{
              x1=-b/(2*a);
  x2=sqrt(-derta)/(2*a);
  printf("two complex roots\n");
  printf("X1=%f+%fi\n",x1,x2);
  printf("X2=%f-%fi\n",x1,x2);

}