include<stdio.h>

include<math.h>

int main() {

int  a,b,c;
scanf("%d %d %d",&a,&b,&c);
double Result=b*b-4.0*a*c;
if(Result>=0)
	{
		printf("Yes\n");
		double x1=(-b+sqrt(Result))/2.0*a;
		double x2=(-b-sqrt(Result))/2.0*a;
		printf("%lf %lf",x1,x2);
	}
else 
	{
		printf("No");
	}		

}

第一，，输出是YES，NO，不是Yes,No 第二，，输出x1,x2时要换行 ， printf("%lf\n%lf",x1,x2); 第三，，要除2a的话，你要么写成(2.0 * a)，要么写成/2.0/a，否则会变成除以2再乘以a

include<stdio.h>

include<math.h>

int main(){

double a,b,c,x1,x2;
scanf("%lf %lf %lf",&a,&b,&c);
double delta=(b*b)-(4*a*c);
if(delta>=0){
	printf("YES\n");
	x1=(-b+sqrt(delta))/(2*a);
	x2=(-b-sqrt(delta))/(2*a);
	printf("%f %f",x1,x2);
}else printf("NO\n");
return 0;

}