namespace Task3

{

    class MainClass

    {

        public static void Main(string[] args)

        {

            const string expression = "((a + b)² - (a² + 2ab)) / b²";

            Console.WriteLine(expression);

​

            var a = GetDouble("a");

            var b = GetDouble("b");

​

            if (b == 0)

            {

                Console.WriteLine("Invalid value of b");

                return;

            }

​

​

            var result = EvaluateExpression(a, b);

​

            Console.WriteLine(@$"a={a};

b = {b};

{expression} = {result}");

        }

​

        private static double GetDouble(string varName)

        {

            Console.WriteLine($"Enter the number '{varName}', using a '.' for fractional part");

            double value;

            while (!double.TryParse(Console.ReadLine(), NumberStyles.Float | NumberStyles.Integer, CultureInfo.InvariantCulture, out value))

                Console.WriteLine("Wrong number format, please try again");

            return value;

        }

​

        private static double EvaluateExpression(double a, double b) =>

         (Math.Pow(a + b, 2) - (Math.Pow(a, 2) + 2 * a * b)) / Math.Pow(b, 2);

​

    }

}