程序代码：

#include<stdio.h>
#include<math.h>
int main()
{
int solve(float,float,float);
float a,b,c,f;
int black;
scanf("%f %f %f",&a,&b,&c);
f = b * b - 4 * a * c;
black = solve(a,b,c);
if(black == 0) printf("无解");
if(black == 1){
    if(a != 0 && b != 0) printf("x1 = x2 = %g",(-b)/(2 * a));
    if(a == 0) printf("x = %g",(-c)/b);
    if(b == 0){
        if((-c)/a < 0) printf("x = -%g",sqrt(c/a));
        else printf("x = %g",sqrt((-c)/a));
    }
}
if(black == 2){
    if(f > 0)
        printf("x1 = %g, x2 = %g",((-b) + sqrt(f))/(2*a),((-b) - sqrt(f))/(2*a));
    if(f < 0)
        if(a < 0) printf("x1 = %g%gi, x2 = %g+%gi",(-b)/(2*a),sqrt(-f)/(2*a),(-b)/(2*a),-sqrt(-f)/(2*a));
        else printf("x1 = %g%gi, x2 = %g+%gi",(-b)/(2*a),sqrt(-f)/(2*a),(-b)/(2*a),-sqrt(-f)/(2*a));
}
if(black == 3) printf("无穷多解");
return 0;
}
int solve(float a,float b,float c)
{
float flag;
flag = b * b - 4 * a * c;
if(((a == 0 && b != 0) || (a != 0 && b == 0)) && c != 0) return 1;
if(a == 0 && b == 0 && c != 0) return 0;
if((a == 0 || b == 0) && c == 0) return 3;
if(flag > 0 && flag < 1E-4) return 1;
if(flag == 0) return 1;
if(flag > 0) return 2;
if(flag < 0) return 2;
if(c == 0 && (a != 0 || b != 0)) return 3;
}