1. **State the problem:** Add the expressions $$- \frac{7}{x^2 + 3x - 10} + \frac{12}{x^2 - 2x - 35}$$.
2. **Factor the denominators:**
$$x^2 + 3x - 10 = (x + 5)(x - 2)$$
$$x^2 - 2x - 35 = (x - 7)(x + 5)$$
3. **Find the common denominator:**
The least common denominator (LCD) is $$ (x + 5)(x - 2)(x - 7) $$.
4. **Rewrite each fraction with the LCD:**
$$- \frac{7}{(x + 5)(x - 2)} = - \frac{7(x - 7)}{(x + 5)(x - 2)(x - 7)}$$
$$\frac{12}{(x - 7)(x + 5)} = \frac{12(x - 2)}{(x + 5)(x - 2)(x - 7)}$$
5. **Add the numerators:**
$$-7(x - 7) + 12(x - 2) = -7x + 49 + 12x - 24 = 5x + 25$$
6. **Write the combined fraction:**
$$\frac{5x + 25}{(x + 5)(x - 2)(x - 7)}$$
7. **Factor numerator:**
$$5x + 25 = 5(x + 5)$$
8. **Simplify by canceling common factor:**
$$\frac{\cancel{5}(x + 5)}{(x + 5)(x - 2)(x - 7)} = \frac{5}{(x - 2)(x - 7)}$$
9. **Rewrite denominator as quadratic:**
$$(x - 2)(x - 7) = x^2 - 9x + 14$$
10. **Final answer:**
$$\frac{5}{x^2 - 9x + 14}$$
This matches option B.
Add Rational Expressions 7F80Ba
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