Информатика тема ветвление

 public static double y(double x) => x < 5 ? (4 * x * x + 1) / (x - 5) : 3 * x * x - 2; 
public static bool IsDivisorOf3(int n) => n == 3 || n == 1; 
public static void NumberReplacement(ref double x, ref double y) 
{ 
    double p = x * y; 
    double s = x + y; 
    if (x    { 
        x = s; 
        y = p; 
        return; 
    } 
    y = s; 
    x = p; 
}