for (int i = 0; i <10; i++)
{

Console.Title = "一元二次方程程序";
double a, b, c, d, x1, x2;

Console.WriteLine("求解一元二次方程ax*x+bx+c=0");
Console.WriteLine("请输入a：");
a = Convert.ToDouble(Console.ReadLine());
if (a == 0)
{
Console.WriteLine("不能为0，否则不是一元二次方程！！");
Console.WriteLine("请重新输入a：");
a = Convert.ToDouble(Console.ReadLine());
}
else
{
Console.WriteLine("请输入b：");
b = Convert.ToDouble(Console.ReadLine());
Console.WriteLine("请输入c：");
c = Convert.ToDouble(Console.ReadLine());
d = b * b - 4 * a * c;

if (d < 0)
{
Console.WriteLine("方程无实解");
}
else
{
x1 = (-b + Math.Sqrt(d)) / (2 * a);
x2 = (-b - Math.Sqrt(d)) / (2 * a);
if (d == 0)
{
Console.WriteLine("方程有两个相同的实根：");
Console.WriteLine("x1=x2=" + x1.ToString());
}
else
{
Console.WriteLine("方程有两个相同的实根：");
Console.WriteLine("x1=" + x1.ToString());
Console.WriteLine("x2=" + x2.ToString());
}
}
Console.WriteLine("按任意键重新开始。");
Console.ReadKey();
}

}