Limit Rational 12C3E2
1. **State the problem:** Find the limit $$\lim_{x \to -3} \frac{4x^2 + 12x}{x^2 + 4x + 3}$$.
2. **Check direct substitution:** Substitute $x = -3$ into numerator and denominator.
Numerator: $$4(-3)^2 + 12(-3) = 4(9) - 36 = 36 - 36 = 0$$
Denominator: $$(-3)^2 + 4(-3) + 3 = 9 - 12 + 3 = 0$$
Since direct substitution gives $\frac{0}{0}$, an indeterminate form, we need to simplify.
3. **Factor numerator and denominator:**
Numerator: $$4x^2 + 12x = 4x(x + 3)$$
Denominator: $$x^2 + 4x + 3 = (x + 3)(x + 1)$$
4. **Simplify the expression:**
$$\frac{4x(x + 3)}{(x + 3)(x + 1)} = \frac{4x}{x + 1}, \quad x \neq -3$$
5. **Evaluate the limit of the simplified expression:**
$$\lim_{x \to -3} \frac{4x}{x + 1} = \frac{4(-3)}{-3 + 1} = \frac{-12}{-2} = 6$$
6. **Conclusion:** The limit is $6$.
**Final answer:** C 6