Simplify the expression $$ (3 + \sqrt{7})(3 - \sqrt{7}) $$ ....

Question Analysis
This problem assesses the understanding of multiplying conjugate binomial radicals and the difference of squares formula.

Key Concept Explanation
When multiplying conjugate binomial radicals, the product of the outer and inner terms cancel out.

Step-by-step Solution
1. Identify the conjugates: and
2. Apply the difference of squares formula: