1. **State the problem:** Simplify the expression $$\frac{7x + 3}{x - 4} + \frac{5x}{x^2 - 16}$$.
2. **Identify the denominators:** The denominators are $x - 4$ and $x^2 - 16$. Note that $x^2 - 16$ is a difference of squares and can be factored:
$$x^2 - 16 = (x - 4)(x + 4)$$
3. **Find the common denominator:** The least common denominator (LCD) is $(x - 4)(x + 4)$.
4. **Rewrite each fraction with the LCD:**
- The first fraction needs to be multiplied by $\frac{x + 4}{x + 4}$:
$$\frac{7x + 3}{x - 4} = \frac{(7x + 3)(x + 4)}{(x - 4)(x + 4)}$$
- The second fraction already has the denominator $(x - 4)(x + 4)$.
5. **Write the sum with the common denominator:**
$$\frac{(7x + 3)(x + 4)}{(x - 4)(x + 4)} + \frac{5x}{(x - 4)(x + 4)} = \frac{(7x + 3)(x + 4) + 5x}{(x - 4)(x + 4)}$$
6. **Expand the numerator:**
$$ (7x + 3)(x + 4) = 7x \cdot x + 7x \cdot 4 + 3 \cdot x + 3 \cdot 4 = 7x^2 + 28x + 3x + 12 = 7x^2 + 31x + 12 $$
7. **Add the remaining term in the numerator:**
$$7x^2 + 31x + 12 + 5x = 7x^2 + 36x + 12$$
8. **Write the full expression:**
$$\frac{7x^2 + 36x + 12}{(x - 4)(x + 4)}$$
9. **Factor the numerator if possible:**
Find factors of $7 \times 12 = 84$ that sum to 36. Factors 6 and 14 sum to 20, 12 and 7 sum to 19, 21 and 4 sum to 25, 28 and 3 sum to 31, 42 and 2 sum to 44, 3 and 28 sum to 31, 6 and 14 sum to 20, 12 and 7 sum to 19, 21 and 4 sum to 25, 28 and 3 sum to 31, 42 and 2 sum to 44, 1 and 84 sum to 85. None sum to 36, so the quadratic does not factor nicely.
10. **Final simplified expression:**
$$\frac{7x^2 + 36x + 12}{(x - 4)(x + 4)}$$
This is the simplified form of the original expression.
Rational Expression Sum 5Aac17
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