题目描述： 

---

AC代码： 

#include<iostream>

using namespace std;

double a,b,c,d;
int ans = 0;

double f(double x)
{
	return a * x * x * x + b * x * x + c * x + d;
}

int main()
{
	scanf("%lf %lf %lf %lf",&a,&b,&c,&d);
	for(double i=-100.00;i<=100.00;i+=0.001)
	{
		double l = i,r = i + 0.001;
		if(f(l) * f(r) < 0)
		{
			printf("%.2lf ",l);
			ans++;
		}
		if(ans == 3) break;
	}
	return 0;
}