How to make calculate quadratic formula in c#

How to make calculate quadratic formula in c#
Object

Write a program which takes two variables a, b and constant c as input from the user to calculate roots using quadratic formula. It must include two functions to return the calculated roots. 

  
Code

    class program1

    {

        Public static double root(double a, double b, double c)

        {

            double re = -b + System.Math.Sqrt(b * b) - (4 * a * c) / (2 * a);

           return re;

        }

    }

    class Program

    {

        static void Main(string[] args)

        {

            ///////////////////////////first//////////////////////////////

            double a, b, c;

            double res = 0;

            Console.WriteLine("Enter a value");

            a = double.Parse(Console.ReadLine());

            Console.WriteLine("Enter B value");

            b = double.Parse(Console.ReadLine());

            Console.WriteLine("Enter c Value");

            c = double.Parse(Console.ReadLine());

           

            res = pogram.root(a, b, c);

            Console.WriteLine("Quadratic Answer is ::" + res);

Screen Shot