квадратур метод

 static void DifferenceMethod()
        {
            double begin = 0;
            double end = 12;
            double[] x = new double[N];
            double[] y = new double[N];
            double[] yt = new double[N];
            double[] e = new double[N];
            double[] p = new double[N + 1];
            double[] q = new double[N + 1];
            double h = end - begin;
            h /= N;
            x[0] = begin;

            for (int i = 1; i < N; i++)
                x[i] = x[i - 1] + h;

            for (int i = 0; i < N; i++)
            {
                double a, b, c, d;

                d = (Math.Pow(x[i], 6) - 12 * Math.Pow(x[i], 5) + 3 * Math.Pow(x[i], 4) - 2 * 12 * Math.Pow(x[i], 3) + 6 * x[i] - 2 * 12) *( h * h) / 2;
                a = 1 / 2 - x[i] * x[i] / 4 * h;
                b = 1 / 2 + h * x[i] * x[i] / 4;
                c = -(-1 + x[i] * x[i] * x[i] / 2 * h);

                if (i == N - 1)     p[i + 1] = 0;
                else   p[i + 1] = b / (c - a * p[i]);

                q[i + 1] = (d + a * q[i]) / (c - a * p[i]);
            }

            for (int i = N - 2; i > 0; i--)
                y[i] = p[i + 1] * y[i+1] + q[i + 1];

            for (int i = 1; i < N - 1; i++)
            {
                yt[i] = Math.Pow(x[i], 3) - 12 * Math.Pow(x[i], 2);
                e[i] = Math.Abs(yt[i]- y[i]);
            }


            Console.WriteLine("Шаг: ");
            foreach(double i in x)
                Console.Write("{0:F5} | ", i);

            Console.WriteLine("\n \n Y:");
            foreach(double i in y)
                Console.Write("{0:F5} | ", i);

            Console.WriteLine("\n \n Y точные:");
            foreach(double i in yt)
                Console.Write("{0:F5} | ", i);

            Console.WriteLine(" \n \n точность");
            foreach(double i in e)
                Console.Write("{0:F5} | ", i);
        }

        static void Main(string[] args)
        {
            DifferenceMethod();
        }