using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace Gradient
{
    class Program
    {
        static Func<double,double>  fx = x => Math.Sqrt(5 * x * x + x + 6) + Math.Sqrt(3 * x + 7);
        static Func<double,double> grad = x => ((10 * x) / (2 * Math.Sqrt(5 * x * x + x + 6))) + 3 / (2 * Math.Sqrt(3 * x + 7));
        static double xOld = 0;
        static double xNew;
        static int kmax = 25000;
        static int k = 1;
        static double A = 0.2;
        static double eps = 0.3;
        static double S = double.MaxValue;

        static void Main(string[] args)
        {
            while (k < kmax && eps < S)
            {
                xNew = xOld - A * grad(xOld);
                S = Math.Abs(xNew - xOld);
                xOld = xNew;
                k++;
            }

            Console.WriteLine($"x = {0}", xOld);
            Console.WriteLine($"f(x) = {0}", fx(xOld));
        }
    }
}