Rational Equations E74F3F
1. **State the problem:** Solve the rational equation $$-\frac{1}{x^2 + 8x} + \frac{9x}{x + 8} = \frac{8}{x + 8}$$ for all values of $x$.
2. **Identify the domain restrictions:** The denominators cannot be zero, so:
- $x^2 + 8x = x(x+8) \neq 0 \implies x \neq 0, x \neq -8$
- $x + 8 \neq 0 \implies x \neq -8$
3. **Rewrite the equation:**
$$-\frac{1}{x(x+8)} + \frac{9x}{x+8} = \frac{8}{x+8}$$
4. **Find a common denominator:** The common denominator is $x(x+8)$.
5. **Express all terms with the common denominator:**
- First term is already $-\frac{1}{x(x+8)}$
- Second term: $$\frac{9x}{x+8} = \frac{9x \cdot x}{x(x+8)} = \frac{9x^2}{x(x+8)}$$
- Third term: $$\frac{8}{x+8} = \frac{8 \cdot x}{x(x+8)} = \frac{8x}{x(x+8)}$$
6. **Combine all terms:**
$$-\frac{1}{x(x+8)} + \frac{9x^2}{x(x+8)} = \frac{8x}{x(x+8)}$$
7. **Multiply both sides by $x(x+8)$ to clear denominators:**
$$-1 + 9x^2 = 8x$$
8. **Rearrange to standard quadratic form:**
$$9x^2 - 8x - 1 = 0$$
9. **Use the quadratic formula:**
$$x = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a}$$ where $a=9$, $b=-8$, $c=-1$.
Calculate the discriminant:
$$\Delta = (-8)^2 - 4 \cdot 9 \cdot (-1) = 64 + 36 = 100$$
10. **Find the roots:**
$$x = \frac{8 \pm \sqrt{100}}{18} = \frac{8 \pm 10}{18}$$
- For $+$:
$$x = \frac{8 + 10}{18} = \frac{18}{18} = 1$$
- For $-$:
$$x = \frac{8 - 10}{18} = \frac{-2}{18} = -\frac{1}{9}$$
11. **Check domain restrictions:**
- $x=1$ is allowed (not 0 or -8)
- $x=-\frac{1}{9}$ is allowed
**Final answer:**
$$x = 1 \text{ or } x = -\frac{1}{9}$$