1. **State the problem:** Solve the equation $$\frac{x}{x-1} + \frac{x}{x+1} - \frac{3}{x-1} = 4$$ using the quadratic formula.
2. **Rewrite the equation:** Move all terms to one side to set the equation equal to zero:
$$\frac{x}{x-1} + \frac{x}{x+1} - \frac{3}{x-1} - 4 = 0$$
3. **Find a common denominator:** The denominators are $x-1$ and $x+1$. The common denominator is $(x-1)(x+1) = x^2 - 1$.
4. **Rewrite each term with the common denominator:**
$$\frac{x(x+1)}{x^2 - 1} + \frac{x(x-1)}{x^2 - 1} - \frac{3(x+1)}{x^2 - 1} - \frac{4(x^2 - 1)}{x^2 - 1} = 0$$
5. **Combine the numerators:**
$$\frac{x(x+1) + x(x-1) - 3(x+1) - 4(x^2 - 1)}{x^2 - 1} = 0$$
6. **Simplify the numerator:**
$$x^2 + x + x^2 - x - 3x - 3 - 4x^2 + 4 = 0$$
7. **Combine like terms:**
$$x^2 + x^2 - 4x^2 + x - x - 3x - 3 + 4 = 0$$
$$(-2x^2) - 3x + 1 = 0$$
8. **Multiply both sides by $-1$ to simplify:**
$$\cancel{-}2x^2 - 3x + 1 = 0 \Rightarrow 2x^2 + 3x - 1 = 0$$
9. **Use the quadratic formula:**
$$x = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a}$$
where $a=2$, $b=3$, and $c=-1$.
10. **Calculate the discriminant:**
$$b^2 - 4ac = 3^2 - 4(2)(-1) = 9 + 8 = 17$$
11. **Write the solutions:**
$$x = \frac{-3 \pm \sqrt{17}}{2 \times 2} = \frac{-3 \pm \sqrt{17}}{4}$$
12. **Final answer:**
$$x = \frac{-3 + \sqrt{17}}{4} \quad \text{or} \quad x = \frac{-3 - \sqrt{17}}{4}$$
These are the two solutions to the original equation, provided they do not make any denominator zero (check $x \neq 1$ and $x \neq -1$). Both solutions are valid since neither equals 1 or -1.
Quadratic Rational Fb8545
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