c语言 求方程ax2+bx+c=0的根，用三个函数分别求当b2-4ac大于0、等于0和小于0时的根，不知道哪错了啊

#include<stdio.h>
#include<math.h>
void fun1(double a, double b, double c)

{
double k=-b/(2*a);

printf("x1=x2=%lf\n",k);

}

void fun2(double a, double b, double c)

{
double d,j1,j2;
d=b*b-4*a*c;
j1=(-b+sqrt(d))/(2*a);
j2=(-b-sqrt(d))/(2*a);

printf("x1=%lf\n",j1);
printf("x2=%lf\n",j2);
}
void fun3(double a, double b, double c)
{
double x3,x4,d;
d=b*b-4*a*c;
x3=-b/(2*a);
x4=sqrt(-d)/(2*a);
printf("x1=%f+%fi\n",x3,x4);
printf("x2=%f-%fi\n",x3,x4);
}
void main()
{

double a,b,c,d;
printf("please enter a,b,c:");
scanf("%f%f%f",&a,&b,&c);
d=b*b-4*a*c;

if(a==0)
{
printf("erro!enter again\n");
return;
}

if (d==0) fun1(a, b, c);
else if (d>0) fun2(a, b, c);
else fun3(a, b, c);

}

相关了解……