If $ | \vec{a} | = 3 $, $ | \vec{b} | = 2 $, then find $ (3\vec{a} - 2\vec{b}) \cdot (3\vec{a} + 2\vec{b}) $.
If \(f(x)\) is continuous in \(\mathbb{R}\),
\[f(x) = \begin{cases} \frac{3x^2 - 12}{x - 2}, & x \neq 2 \\k, & x = 2 \end{cases}\]find \(k\).
If $ | \vec{a} | = 3 $, $ | \vec{b} | = 2 $, then find $ (3\vec{a} - 2\vec{b}) \cdot (3\vec{a} + 2\vec{b}) $.