public static void Main()
Console.WriteLine("He phuong trinh dang: a*x*x + b*x + c = 0");
Console.Write("Nhap a: ");
a = double.Parse(Console.ReadLine());
Console.Write("Nhap b: ");
b = double.Parse(Console.ReadLine());
Console.Write("Nhap c: ");
c = double.Parse(Console.ReadLine());
double d = (b * b) - (4 * a * c);
Console.WriteLine("He phuong trinh tren vo nghiem");
double x = (-b) / (2 * a);
Console.WriteLine("He phuong trinh co nghiem kep la: {0}", x);
double x1 = ((-b) + Math.Sqrt(d)) / (2 * a);
double x2 = ((-b) - Math.Sqrt(d)) / (2 * a);
Console.WriteLine("He phuong trinh co 2 nghiem:");
Console.WriteLine("x1 = {0}", x1);
Console.WriteLine("x2 = {0}", x2);