//IamQuan :3

//Libraly
#include<iostream>
#include <math.h>
using namespace std;
//Code
//Ham Phu de goi an cho a b c
double GoiAn()
{
	double ABC{};
	std::cin >> ABC;
	return ABC;
}
//Code
int main()
{
	//Khai bao cho DK
	int A{};
	//Khai bao cho tinh toan
	double x1, x2;
//--------------------------------------------------
	// User nhap a b c
	cout << "Chuong trinh tinh phuong trinh bac 2 mot an\n";
	cout << "Vui long nhap cac he so a , b , c\n";
	cout << "---------------------------------------------" << endl;
	//Nhap he so a
	cout << "Nhap he so a: " ;
	double a{GoiAn()};

	//Dieu kien
	while (a == 0 && A < 1000)
	{
		cout << "Phuong trinh da chuyen ve \nphuong trinh bac nhat mot an" << endl;
		cout << "Ban co muon nhap lai ham so a ?\nNeu muon thi nhap lai.\na:" << endl;
		cin >> a;
		A++;
	}
	//Nhap he so b
	cout << "Nhap he so b: ";
	double b{ GoiAn() };

	//Nhap he so c
	cout << "Nhap he so c: ";
	double c{ GoiAn() };

	// Thong bao cho user
	cout << "Dang tinh delta va nghiem ......." << endl;
	
	//Khai bao Delta
	double delta{ (b * b) - 4 * a * c }; 
	 //Tinh delta
	if (delta < 0)
	{
		cout << "Delta = " << delta << "\n";
		cout << " => Phuong trinh vo nghiem " << endl;
	}
	else if (delta == 0)
	{
		cout << "Delta = " << delta << "\n";
		cout << " => Phuong trinh co nghiem kep " << endl;
	}
	else if (delta > 0)
	{
		cout << "Delta = " << delta << "\n";
		cout << " => Phuong trinh co 2 nghiem phan biet " << endl;
	}
	cout << "\n\n";

	//Tinh nghiem
	if (delta > 0)
	{
		x1 = (-b - sqrt(delta)) / (2 * a);
		x2 = (-b + sqrt(delta)) / (2 * a);

		cout << "Nghiem cua phuong trinh la: \n";
		cout << "x1 = " << x1 << endl;
		cout << "x2 = " << x2 << endl;
	}
	else if (delta == 0) {
		x1 = x2 = -b / (2 * a);
		cout << "Nghiem cua phuong trinh la: \n";
		cout << "x1 = x2 = " << x1 << endl;
	}
	else
	{
		cout << "Vi phuong trinh vo nghiem nen khong co nghiem" << endl;
	}
	system("pause");
	return 0;
}