C :

#include<stdio.h>
#include"math.h"  
float yishigen(m,n,k)  
float m,n,k;  
{float x1,x2;  
x1=(-n+sqrt(k))/(2*m);  
x2=(-n-sqrt(k))/(2*m);  
printf("x1=%.3f x2=%.3f\n",x1,x2);  
}  
float denggen(m,n)  
float m,n;  
{float x;  
x=-n/(2*m);  
printf("x1=%.3f x2=%.3f\n",x,x);  
}  
float xugen(m,n,k)  
float m,n,k;  
{float x,y;  
x=-n/(2*m);  
y=sqrt(-k)/(2*m);  
printf("x1=%.3f+%.3fi x2=%.3f-%.3fi\n",x,y,x,y);  
}  
main()  
{float a,b,c,q;  
//printf("input a b c is ");  
scanf("%f%f%f",&a,&b,&c);  
//printf("\n");  
q=b*b-4*a*c;  
if(q>0) yishigen(a,b,q);  
else if(q==0) denggen(a,b);  
else xugen(a,b,q);  
}

C++ :

#include <iostream>
#include <stdio.h>
//#include <conio.h>
#include <math.h>
using namespace std;

int main()
{
	double a,b,c,k,a1,a2;
	cin >> a >> b >> c;
	k = b*b-4*a*c;
	if (k>0) {
		a1 = (-b+sqrt(k))/(2*a);
		a2 = (-b-sqrt(k))/(2*a);
		cout << "x1=" << a1 << " x2=" << a2;
	} else if (k==0){
		a1 = -b/(2*a);
		cout << "x1=" << a1 << " x2=" << a1;
	} else {
		a1 = -b/(2*a);
		a2 = sqrt(-k)/(2*a);
		//cout << "x1=" << a1 << "+" << a2 << "i x2=" << a1 << "-" << a2 << "i";
		printf("x1=%.3f+%.3fi x2=%.3f-%.3fi",a1,a2,a1,a2);
	}
	//_getch();
	return 0;
}

Java :

import java.util.Scanner;

public class Main {

	/**
	 * @param args
	 */
	public static void main(String[] args) {
		// TODO Auto-generated method stub
		Scanner input = new Scanner(System.in);
		
		int a = input.nextInt();
		int b = input.nextInt();
		int c = input.nextInt();
		double x1,x2;
		if(b*b > 4*a*c){
			x1 = (-b + Math.sqrt(b*b - 4*a*c))/(2.0*a);
			x2 = (-b - Math.sqrt(b*b - 4*a*c))/(2.0*a);
			System.out.printf("x1=%.3f x2=%.3f",x1,x2);
		}else if(b*b == 4*a*c){
			x1 = x2 = (-b/(2.0*a));
			System.out.printf("x1=%.3f x2=%.3f",x1,x2);
		}else{
			x1 = (-b/(2.0*a));
			x2 = (Math.sqrt(4*a*c - b*b))/(2.0*a);
			System.out.printf("x1=%.3f+%.3fi x2=%.3f-%.3fi",x1,x2,x1,x2);
		}
		
		input.close();
	}

}

Python :

a = map(lambda x:float(x), raw_input().split())

b = a[1]
c = a[2]
a = a[0]

def f(x):
    if x>=0:
        return '+'
    else:
        return ''


delta = b**2 - 4*a*c
if delta > 0:
    x1 = "%.3f"%((-b+delta**0.5)/(2*a))
    x2 = "%.3f"%(-b-delta**0.5)/(2*a)
else :
    x1 = "x1=%.3f%s%.3fi"%(-b/(2*a),f((-delta)**0.5/(2*a)), (-delta)**0.5/(2*a))
    x2 = "x2=%.3f%s%.3fi"%(-b/(2*a),f(-(-delta)**0.5/(2*a)), -(-delta)**0.5/(2*a))

print x1,x2