static void Main(string[] args) { { double coefficientA = 0; double coefficientB = 0; double coefficientC = 0; Console.WriteLine("quadratic equation: ax2 + bx + c = 0"); Console.Write("a = "); while (!double.TryParse(Console.ReadLine(), out coefficientA)) { Console.WriteLine("Input Error! Insert number"); } Console.Write("b = "); while (!double.TryParse(Console.ReadLine(), out coefficientB)) { Console.WriteLine("Input Error! Insert number"); } Console.Write("c = "); while (!double.TryParse(Console.ReadLine(), out coefficientC)) { Console.WriteLine("Input Error! Insert number"); } string result = string.Empty; if (coefficientA == 0) { result = "This is not a quadratic equation"; } else { if (coefficientB == 0 || coefficientC == 0) { result = Calculator.nQuadraticEquation(coefficientA, coefficientB, coefficientC, result); } else { result = Calculator.quadraticEquation(coefficientA, coefficientB, coefficientC, result); } } Console.WriteLine(result); Console.ReadKey(); } }