Limit Rational 5F5Fa5
1. **State the problem:** Find the limit $$\lim_{x \to 3} \frac{6 + x - x^2}{12 - x - x^2}$$.
2. **Recall the limit rule:** If direct substitution leads to an indeterminate form like $$\frac{0}{0}$$, try to simplify the expression.
3. **Substitute $x=3$ directly:**
$$\frac{6 + 3 - 3^2}{12 - 3 - 3^2} = \frac{6 + 3 - 9}{12 - 3 - 9} = \frac{0}{0}$$ which is indeterminate.
4. **Factor numerator and denominator:**
- Numerator: $$6 + x - x^2 = -x^2 + x + 6 = -(x^2 - x - 6)$$
- Factor inside parentheses: $$x^2 - x - 6 = (x - 3)(x + 2)$$
- So numerator: $$-(x - 3)(x + 2)$$
- Denominator: $$12 - x - x^2 = -x^2 - x + 12 = -(x^2 + x - 12)$$
- Factor inside parentheses: $$x^2 + x - 12 = (x - 3)(x + 4)$$
- So denominator: $$-(x - 3)(x + 4)$$
5. **Simplify the fraction:**
$$\frac{-(x - 3)(x + 2)}{-(x - 3)(x + 4)} = \frac{(x - 3)(x + 2)}{(x - 3)(x + 4)}$$
Cancel out the common factor $(x - 3)$ (valid since $x \to 3$, $x \neq 3$):
$$= \frac{x + 2}{x + 4}$$
6. **Evaluate the simplified limit:**
$$\lim_{x \to 3} \frac{x + 2}{x + 4} = \frac{3 + 2}{3 + 4} = \frac{5}{7}$$
**Final answer:** $$\boxed{\frac{5}{7}}$$