语句练习

            //a1.方程x^2+bx+c=0;一元二次方程。求根
            //△=b^2-4ac；若△<0方程无实根
            //若△>0，方程有两个不相同的实根x1   x2
            ////若△=0，方程有两个相同的实根
            
            Console.WriteLine("请输入a=");
            double a = double.Parse(Console.ReadLine());
            if (a != 0)
            {
                Console.WriteLine("请输入b=");
                double b = double.Parse(Console.ReadLine());
                Console.WriteLine("请输入c=");
                double c = double.Parse(Console.ReadLine());
                double d = b * b - 4 * a * c;

                if (d > 0)
                {
                    double x1 = (-b + Math.Sqrt(d)) / (2 * a);
                    double x2 = (b + Math.Sqrt(d)) / (2 * a);

                    Console.WriteLine("此方程有两个实数根x1={0},x2={1}",x1,x2);
                }
              else  if (d == 0)
                {
                    double x = (-b + Math.Sqrt(d)) / (2 * a);
                    Console.WriteLine("此方程有一个根x="+ x);
                }
           

            else
            { Console.WriteLine("这个方程无解"); }}

            Console.ReadLine();

 //2.有一组函数：
            //y = x (x<1)；
            //y = 2x -1  (1<=x<10)；
            //y = 3x-11  (x>=10)。
            //括号内是x的满足条件。
            //实现功能，随意输入一个x值，输出y的值
            Console.WriteLine("请输入x的值");
            double x = double.Parse(Console.ReadLine());
            double y = x;
           
            if (x < 1)
            {
                Console.WriteLine("y="+ y);

            }
            else if (x >= 1 && x < 10) { Console.WriteLine("y="+ (2 * x - 1)); }
            else
            {
                Console.WriteLine("y="+(3 * x - 11));
            }
            Console.ReadLine();

            //3.输入整数a和b,若a^2+b^2大于100,
            //则输出a^2+b^2百位以上数字,否则输出两数之和

            Console.WriteLine("请输入a=");
            int a =int .Parse ( Console.ReadLine());
            Console.WriteLine("请输入b=");
            int b = int.Parse(Console.ReadLine());
            if (a * a + b * b > 100)
            {
                Console.WriteLine(a * a + b * b);
            }
            else { Console.WriteLine(a + b); }
            Console.ReadLine();

            //4.相亲过程：你有房子么？你有钱么？你有能力么？
            //【结婚吧】【先买房子再结婚】【先赚钱再买房子再结婚】都没有【拜拜~~】
            //利用if嵌套做相亲过程
            Console.WriteLine("你有房子么？");
            string a = Console.ReadLine();
            if (a == "有")
            {
                Console.WriteLine("结婚吧");
            }
            else { Console.WriteLine("你有钱吗？"); }
            a = Console.ReadLine();
            if (a=="有"){Console .WriteLine ("先买房子在结婚");}
            else  {Console .WriteLine ("你有能力么？");}
            a = Console.ReadLine();

            if (a == "有") { Console.WriteLine("先赚钱再买房子在结婚"); }

            else

            { Console.WriteLine("拜拜"); }

            Console.ReadLine();