C#编写的应用程序（求根运算）

int a; int b; int c; double x1; double x2; a = Int16.Parse(textBox1.Text); b = Int16.Parse(textBox2.Text); c = Int16.Parse(textBox3.Text); x1 =(-b + System.Math.Sqrt(Convert.ToDouble (b * b - 4 * a * c))) /(2 * a); x2 =(-b -System.Math.Sqrt(Convert.ToDouble(b * b - 4 * a * c))) /(2 * a); textBox4.Text =x1.ToString(); textBox5.Text= x2.ToString();