解一元二次方程

//一元二次方程求解
//重复执行，直到按ctrl+D或ctrl+E 结束
//
#include<math.h>
#include<stdio.h> 
#include<stdlib.h>
int main(){
    float a,b,c,x1,x2;
    float delta,real,imag;
    printf("Enter a,b,c:");
    while(scanf("%f%f%f",&a,&b,&c)){
        if(a==0)
            printf("not quadratic equation.\n");
        else{
            delta=b*b-4*a*c;
            if(delta>=0){
                x1=(-b+sqrt(delta))/(2*a);
                x2=(-b+sqrt(delta))/(2*a);
                printf("x1=%f,x2=%f\n",x1,x2);
            }
            else{
                real=-b/(2*a);
                imag=sqrt(-delta)/(2*a);
                printf("x1=%f+%fi,x2=%f-%fi\n",real,imag,real,imag);
            }
        }
        printf("Enter a,b,c:\n");
    }
    system("pause");
    return 0;
}