ïżusing System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace ConsoleApplication1
{
class Program
{
static void Main(string[] args)
{

double a, b, c, delta, x1, x2;

Console.WriteLine("Podaj współczynniki równania kwadratowego:");
Console.Write("a="); a = double.Parse(Console.ReadLine());
Console.Write("b="); b = double.Parse(Console.ReadLine());
Console.Write("c="); c = double.Parse(Console.ReadLine());

delta = (b * b) - (4 * a * c);
if (delta >= 0)
{
x1 = (-b - Math.Sqrt(delta)) / (2 * a);
x2 = (-b + Math.Sqrt(delta)) / (2 * a);
Console.WriteLine("x1=" + x1);
Console.WriteLine("x2=" + x2);
}
else
{
x1 = -b / (2 * a);
x2 = Math.Sqrt(-delta) / (2 * a);
Console.WriteLine("x1=" + x1 + "+j" + x2);
Console.WriteLine("x2=" + x1 + "-j" + x2);
}

Console.ReadKey();
}
}
}

x2 = Math.Sqrt(-delta) / (2 * a)
x2 = Math.Sqrt(math.abs(delta)) / (2 * a)