private void button3_Click(object sender, EventArgs e)
    {
      double eps = 1e-10;
      int itmax = 100;
      //double [,]deltax ;

      double[,] x = { { 1 }, { 1 }, { 1 }, { 1  } };
      Matrix<double> X = Matrix<double>.Build.DenseOfArray(x);

      // Matrix<double> delt = Matrix<double>.Build.DenseOfArray(x);
      for (int i = 1; i <= itmax; i++)
      {
        double[,] delta;
        Matrix<double> _df = Matrix<double>.Build.DenseOfArray(_DF(X.ToArray()));

        Matrix<double> f = Matrix<double>.Build.DenseOfArray(F(X.ToArray()));
        delta = Accord.Math.Matrix.Divide(_df.ToArray(), f.ToArray());
        Matrix<double> deltax = Matrix<double>.Build.DenseOfArray(delta);
        deltax =_df.Inverse() * f;


         X = X + deltax;
        double tikslumas = deltax.L2Norm()/(X.L2Norm()+deltax.L2Norm());
        richTextBox1.AppendText(string.Format("\n iteracija{0}  tikslumas {1}",i,tikslumas));
        if (tikslumas < eps)
        {
          richTextBox1.AppendText(string.Format("\n sprendinys x = {0}", X.ToString()));
          richTextBox1.AppendText(string.Format("\n funkcijos reiksme f = {0}", f.ToString()));
          return;
        }
        else if (i == itmax)
        {
          richTextBox1.AppendText(string.Format("\n ****tikslumas nepasiektas. Paskutinis artinys x = {0}", X.ToString()));
          richTextBox1.AppendText(string.Format("\n funkcijos reiksme f = {0}", f.ToString()));
        }
      }

    }

    private double[,] F(double[,] X)
    {
      double[,] miau = { { 2*X[0,0] + 4* X[1,0] + 2*X[2,0] + 2 * X[3,0] - 20 },
                         { X[1,0]*X[1,0] -X[3,0]*X[3,0] + 32 },
                        { -2*X[0,0]*X[0,0] + 5* X[3,0]*X[3,0]*X[3,0] + 2*X[1,0]*X[3,0] - 1032 },
                        { 4*X[0,0] - 12* X[1,0] + 4*X[2,0] - 3 * X[3,0] + 42 }
                       };
      return miau;
    }
    private double[,] DF(double[] X)
    {
      double[,] miau = { { 2 , 4  , 2 , 2  },
                        { 0 ,2*X[1], 0, -2*X[3] },
                        { -4*X[0] ,2*X[3], 0, 2*X[1]+3*X[3]},
                        { 4,-12, 4 ,-3},
                      };
      return miau;
    }
    private double[,] _DF(double[,] X)
    {
      double[,] miau = { { -2 , -4  , -2 , -2  },
                        { 0 ,-2*X[1,0], 0, 2*X[3,0] },
                        { 4*X[0,0] ,-2*X[3,0], 0, -(2*X[1,0]+3*X[3,0])},
                        { -4,12, -4 ,3},
                      };
      return miau;
    }