C :

#include<stdio.h>
float a,b,c,d;
float f(float x)
{
    return (a*x*x*x+b*x*x+c*x+d);
}
int main()
{
    float x1,x2;
    scanf("%f%f%f%f",&a,&b,&c,&d);
    float x=-100;
    int s=0;
    x1=f(x);
    x2=f(x+0.001);
    while(s<3)
    {
        if(x1*x2<=0)
        {
            if(s!=2)
            printf("%0.2f ",x+0.001);
            if(s==2)
            printf("%0.2f\n",x+0.002);
            s++;
        }
            x=x+0.001;
            x1=x2;
            x2=f(x+0.001);
    }
    printf("\n");
    return 0;
}

C++ :

#include<iostream>
#include<cstdio>
#include<cstring>
#include<string>
#include<cstdlib>
#include<cmath>
#include<iomanip>
#include<algorithm>
using namespace std;
double a,b,c,d;
int k=0;
int main(){
	scanf("%lf%lf%lf%lf",&a,&b,&c,&d);
	//cin>>a>>b>>c>>d;
	double x,temp;
	for(x=-100*1.0;x<=1.0*100;x=1.0*0.01+1.0*x){
		temp=1.0*(a*x*x*x+b*x*x+c*x+d);
		if(temp==0.0||(temp>=-0.001&&temp<=0.001)) {
			k++;
			printf("%.2f",x);
			if(k!=3) cout<<" ";
			else break;
		}
	}
	
	return 0;
}

Java :

import java.math.BigDecimal;
import java.math.RoundingMode;
import java.util.Scanner;
public class Main{
	public static void main(String[] args) {
		Scanner sc=new Scanner(System.in);
		while(sc.hasNext()) {
			double a=sc.nextDouble();
			double b=sc.nextDouble();
			double c=sc.nextDouble();
			double d=sc.nextDouble();
			for(long i=-10000;i<=10000;i++) {
				double z=a*i*i*i+b*i*i*100+c*i*10000+d*1000000;
				int y=(int) z;
				if(y==0) {
					double s=i;
					s=s/100;
					System.out.print(String.format("%.2f ", s) );
				}
			}
			System.out.println();
		}
	}
}