---

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;

namespace WindowsFormsApp5
{
    public partial class Form1 : Form
    {
        double a = 0;
        double b = 0;
        double c = 0;
        double D = 0;
        double x1 = 0;
        double x2 = 0;
        public Form1()
        {
            InitializeComponent();
        }

        private void Form1_Load(object sender, EventArgs e)
        {

        }

        private void button1_Click(object sender, EventArgs e)
        {
            button2.Enabled = true;
            button1.Enabled = false;
            
            try
            {
                a = Convert.ToDouble(textBox1.Text);
                textBox1.Enabled = false;
            }
            catch
            {
                MessageBox.Show("Введите пожалуйста цифры.");
                textBox1.Text = "";
                textBox1.Enabled = true;
                textBox2.Enabled = true;
                textBox3.Enabled = true;
                button1.Enabled = true;
                button2.Enabled = false;
            }
            b = Convert.ToDouble(textBox2.Text);
            c = Convert.ToDouble(textBox3.Text);
            textBox1.Enabled = true;
            textBox4.Visible = true;
            D = Math.Pow(b, 2) - (4 * a) * c;
            textBox4.Text = Convert.ToString(D);
            if (D > 0)
            {
                x1 = (-b - Math.Sqrt(D)) / (2 * a);
                x2 = (-b + Math.Sqrt(D)) / (2 * a);
                textBox5.Text = Convert.ToString(x1);
                textBox6.Text = Convert.ToString(x2);

            }
            else if (D == 0)
            {
                x1 = -b / (2 * a);
                textBox5.Text = Convert.ToString(x1);
            }
            else
            {

            }
        }

        private void button2_Click(object sender, EventArgs e)
        {
            button1.Enabled = true;
            button2.Enabled = false;
            textBox1.Text = "";
            textBox2.Text = "";
            textBox3.Text = "";
            textBox1.Enabled = true;
            textBox2.Enabled = true;
            textBox3.Enabled = true;
            textBox4.Text = "";
            textBox5.Text = "";
            textBox6.Text = "";
        }

        private void textBox1_TextChanged(object sender, EventArgs e)
        {

        }

        private void textBox2_TextChanged(object sender, EventArgs e)
        {

        }

        private void textBox3_TextChanged(object sender, EventArgs e)
        {

        }

        private void label4_Click(object sender, EventArgs e)
        {

        }

        private void textBox5_TextChanged(object sender, EventArgs e)
        {

        }

        private void textBox4_TextChanged(object sender, EventArgs e)
        {

        }

        private void textBox6_TextChanged(object sender, EventArgs e)
        {

        }

        private void label10_Click(object sender, EventArgs e)
        {

        }

        private void label11_Click(object sender, EventArgs e)
        {

        }

        private void label12_Click(object sender, EventArgs e)
        {

        }
    }
}