public static Polynomial Multiply(Polynomial p, double a) => p * a;
 public static Polynomial Multiply(double a, Polynomial p) => a * p;
 public static Polynomial Subtract(Polynomial p1, Polynomial p2) => p1 - p2;
 public static Polynomial Multiply(Polynomial p1, Polynomial p2) => p1 * p2;
 public static Polynomial Add(Polynomial p1, Polynomial p2) => p1 + p2;