CSMath_Exp_Quadratic

using System;
using System.Collections.Generic;
using System.Text;

namespace SoftwareAndFinance
{
    class Math
    {
        const double PI = 3.14159265;
        const double EulersNumber = 2.71828;

        // exp(x) series = 1 + x + x^2 / 2! + x^3 / 3! + x^4 / 4!
        static public double MyExp1(double x)
        {
            double f = x;
            double result = 1 + x;
            double fact = 1;
            int i = 0;
            for (i = 2; i < 20; i++)
            {
                fact *= i;
                f *= x;
                result += f / fact;
            }
            return result;
        }

        // exp(x) series = power(2.71828, x)
        public static double MyExp2(double x)
        {
            return System.Math.Pow(EulersNumber, x);
        }

        // 6x^2 + 11x - 35 = 0 | SolveQuadratic(6, 11, -35);
        // quadratic equation is a second order of polynomial equation in a single variable
        // x = [ -b +/- sqrt(b^2 - 4ac) ] / 2a
        public static void SolveQuadratic(double a, double b, double c)
        {
            double sqrtpart = b * b - 4 * a * c;
            double x, x1, x2, img;
            if (sqrtpart > 0)
            {
                x1 = (-b + System.Math.Sqrt(sqrtpart)) / (2 * a);
                x2 = (-b - System.Math.Sqrt(sqrtpart)) / (2 * a);
                Console.WriteLine("Two Real Solutions: {0,8:f4} or  {1,8:f4}", x1, x2);
            }
            else if (sqrtpart < 0)
            {
                sqrtpart = -sqrtpart;
                x = -b / (2 * a);
                img = System.Math.Sqrt(sqrtpart) / (2 * a);
                Console.WriteLine("Two Imaginary Solutions: {0,8:f4} + {1,8:f4} i or {2,8:f4} + {3,8:f4} i", x, img, x, img);
            }
            else
            {
                x = (-b + System.Math.Sqrt(sqrtpart)) / (2 * a);
                Console.WriteLine("One Real Solution: {0,8:f4}", x);
            }
        }

        static void Main()
        {
            for (double i = -2; i <= 3; i += 0.2)
            {
                Console.WriteLine("{0,8:f2} = {1,8:f4}  {2,8:f4}  {3,8:f4}", i, System.Math.Exp(i), MyExp1(i), MyExp2(i));
            }

            Console.WriteLine();
            Console.WriteLine();


            // 6x^2 + 11x - 35 = 0
            SolveQuadratic(6, 11, -35);

            // 5x^2 + 6x + 1 = 0
            SolveQuadratic(5, 6, 1);

            // 2x^2 + 4x + 2 = 0
            SolveQuadratic(2, 4, 2);

            // 5x^2 + 2x + 1 = 0
            SolveQuadratic(5, 2, 1);

            Console.WriteLine();
            Console.WriteLine();
            Console.ReadLine();
        }
    }
}
// Note: found on the Internet