private void button1_Click(object sender, EventArgs e)
        {
            BackgroundImage = DrawGraphik.Function(40, 15, 400, 400);

            MethChord.Enabled      = true;
            MethTanget.Enabled     = true;
            CombinedMeth.Enabled   = true;
            MethHalfDiv.Enabled    = true;
            MethSimpleIter.Enabled = true;
        }
        private void CombinedMeth_Click(object sender, EventArgs e)
        {
            if (GetAandB())
            {
                Result.Text          = "f(x) = 0 ";
                NumberIteration.Text = "Итераций -  ?";

                float a = Convert.ToSingle(A.Text),
                      b = Convert.ToSingle(B.Text);
                BackgroundImage = DrawGraphik.MethodCombined(DrawGraphik.Function(40, 15, 400, 400), ref a, ref b);
                Result.Text     = Result.Text.Remove(2, 1);
                Result.Text     = Result.Text.Insert(2, b.ToString());

                NumberIteration.Text = NumberIteration.Text.Remove(NumberIteration.Text.Length - 1);
                NumberIteration.Text = NumberIteration.Text.Insert(NumberIteration.Text.Length - 1, a.ToString());
            }
        }