[填空题]
Let f(x)=9-2 $\ln \left(x^{2}+4\right)$ , for $x \in \mathbb{R}$ . The graph of f passes through the point (p, 3) , where p>0 .
1. Find the value of p .
The following diagram shows part of the graph of f .
The region enclosed by the graph of f , the x -axis and the lines x=-p and x=p is rotated $360^{\circ}$ about the x -axis.
2. Find the volume of the solid formed.
