Simplifying a Rational Expression and Evaluating at a Point

Consider the rational expression given by $$ f(x) = \frac{x^2 - 4}{x^2 - x - 6} $$.

First, simplify the rational expression by factoring both the numerator and denominator. After simplification, determine the value of $$ f \left( 3 \right) $$.

Provide the answer in decimal form in the grid below.