If $X = \left\{ 4 ^ { n } - 3 n - 1 : n \in N \right\}$ and $Y = \{ 9 ( n - 1 ) : n \in N \}$, where $N$ is the set of natural numbers, then $X \cup Y$ is equal to (1) $X$ (2) $Y$ (3) $N$ (4) $Y - X$
If $X = \left\{ 4 ^ { n } - 3 n - 1 : n \in N \right\}$ and $Y = \{ 9 ( n - 1 ) : n \in N \}$, where $N$ is the set of natural numbers, then $X \cup Y$ is equal to\\
(1) $X$\\
(2) $Y$\\
(3) $N$\\
(4) $Y - X$