public  class SecondMethod
    {
        protected double a, b, epsilon, n_iteration, c, count = 1;
        protected Form2 form;
        protected Argument x_epresion;
        protected Expression e;
        string expression;
        public SecondMethod(string expression, Form2 form, double a, double b, double epsilon) { 
        
            this.a = a;
            this.b = b;
            this.epsilon = epsilon;
            this.expression = expression;
            this.form = form;
        }
        public double f(double x)
        {
            x_epresion = new Argument("x",x);
            e = new Expression(expression, x_epresion);
         //   this.form.textBox3.AppendText("UWAGA pochodna wynosi"+ directive(1));
            return e.calculate();
        }
        double directive(double f_value)
        {
            Argument x_epresion = new Argument("x", f_value);
            string a = "der(" + e.getExpressionString() + ", x)";


            Function f = new Function("f(x) = " + a);
            e = new Expression("f(" + f_value.ToString() + ")", f);


            e = new Expression(a, x_epresion);
            return e.calculate();
        }
        public virtual double search()
        {
            do
            {
                if (f(a) == f(b))
                {
                    return -1;
                }
                c = (a * f(b) - b * f(a)) / (f(b) - f(a));
                this.form.textBox3.AppendText("pochodna wynosi " + f(c).ToString());
                a = b;
                b = c;
                var napis = String.Format("Iteration {0}    x={1}\n", count, c, 2);
                this.form.textBox2.AppendText(napis);
                count++;
                if (count == 100)
                {
                    return c;
                }

            } while (Math.Abs(f(c)) > epsilon);
            return c;
        }
    }