varible is being used without being initialized

varible is being used without being initialized
#include
#include
double main(void)
{
double a,b,c,d,x1,x2;
printf("enter a:\n");
scanf("%lf",&a);
printf("enter b:\n");
scanf("%lf",&b);
printf("enter c:\n");
scanf("%lf",&c);
d=b*b-4*a*c;
if(d>0)
{
void 函数1(double a,double b,double d,double x1,double x2);
函数1(a,b,d,x1,x2);
}
else if(d