Determine Whether the Set Is fiNite or Infinite $$\left\{ x \mid x \in \mathbf { N } \text { and } 9 x ^ { 2 } - 1 = 0 \right\}$$

Short Answer

determine whether the set is finite or infinite. If the set is finite, find its size.
- $$\left\{ x \mid x \in \mathbf { N } \text { and } 9 x ^ { 2 } - 1 = 0 \right\}$$