3月15日 传址

 public void Fangcheng(double a,double b,double c,out double x1,out double x2) 
        {
            double de = b * b - 4 * a * c;
            if (de > 0)
            {
                Console.WriteLine("此方程有两个不相同的实数根");
                 x1 = -b + Math.Sqrt(de) / (2 * a);
                 x2 = -b - Math.Sqrt(de) / (2 * a);
            }
            else 
            {
                Console.WriteLine("有两个相同的实数根" );
                 x1 = -b + Math.Sqrt(de) / 2 * a;
                 x2 = x1;
            }
        }
 static void Main(string[] args)
        {
 //一元二次方程，传出x1,x2
            double x1;
            double x2;
            Console.WriteLine("求解二元一次方程ax^2+b*x+c=0根的情况及结果");
            Console.Write("请输入a=");
            double a = double.Parse(Console.ReadLine());
            Console.Write("请输入b=");
            double b =double.Parse(Console.ReadLine()); 
            Console.Write("请输入c=");
            double c = double.Parse(Console.ReadLine());        
            double de = b * b - 4 * a * c;
            if (a == 0)
            {
                Console.WriteLine("这个方程不是一元二次方程");
            }
            else
            {
                if (de < 0)
                {
                    Console.WriteLine("没有实数根");
                }
                else 
                {
                    Program pp = new Program();
                    pp.Fangcheng(a,b,c,out x1,out x2);
                    if(x1==x2)
                    {
                        Console.WriteLine("x1=x2="+x1);
                    }
                    else
                    {
                        Console.WriteLine("x1="+x1);
                        Console.WriteLine("x2"+x2);
                    }
                }
            }

            Console.ReadLine();
}