#include <isostream>

#include <cmath>

using namespace std; 

 /**

 * giai phuong trinh bac 2: ax2 + bx + c = 0

 *

 * @param a: he so bac 2 

* @param b: he so bac 1 

* @param c: so hang tu do 

*/

void giaiPTBac2(float a, float b, float c) {

    // kiem tra cac he so    

if (a == 0) {

if (b == 0) {

printf("Phuong trinh vo nghiem!");       

} else {            

printf("Phuong trinh co mot nghiem: x = %f", (-c / b));        

}        

return;    

}   

 // tinh delta    

float delta = b*b - 4*a*c;   

 float x1;    

float x2;   

 // tinh nghiem   

 if (delta > 0) { 

x1 = (float) ((-b + sqrt(delta)) / (2*a));        

x2 = (float) ((-b - sqrt(delta)) / (2*a));        

printf("Phuong trinh co 2 nghiem la: x1 = %f va x2 = %f", x1, x2);   

 } else if (delta == 0) {

        x1 = (-b / (2 * a));        

printf("Phong trinh co nghiem kep: x1 = x2 = %f", x1);    

} else {        

printf("Phuong trinh vo nghiem!");    

}

}

/**

* ham main

*/

int main() {

float a, b, c;    

cout << "Nhap he so bac 2, a = ";    

cin >> a;    

cout << "Nhap he so bac 1, b = ";    

cin >> b;    

cout << "Nhap so hang tu do, c = ";   

 cin >> c;    

giaiPTBac2(a, b, c);   

 return 1;

}

#include <iostream>

#include <conio.h>

#include <math.h>

using namespace std;

 int main()

{     

float a, b, c, delta, x1, x2;

    cout << "Nhap a = ";  

  cin >> a;   

 cout << "Nhap b = ";   

 cin >> b;    

cout << "Nhap c = ";    

cin >> c;  

  if(a == 0) {      

  // a== 0 phuong trinh tro thanh phuong trinh bac mot bx + c = 0  

      if(b == 0) {           

 if (c == 0) {              

  cout << "Phuong trinh vo so nghiem" << endl;    

        } else {             

   cout << "Phuong trinh vo nghiem" << endl;   

         }  

      } else {          

  cout << "Phuong trinh co nghiem duy nhat: " << -c/b << endl;      

  }   

 } else {        

delta = b*b - 4*a*c;      

  if(delta > 0) {      

      x1 = (-b+sqrt(delta))/(2*a);          

  x2 = (-b-sqrt(delta))/(2*a);        

    cout << "Nghiem thu nhat x1 = " << x1 << endl;          

  cout << "Nghiem thu hai x2 = " << x2 << endl;  

      } else if ( delta == 0) {          

  cout << "Phuong trinh co nghiem kep: x1 = x2 = " << -b/2*a << endl;    

    } else {           

 cout << "Phuong trinh vo nghiem" << endl;    

    }    

}   

 return 0;

}