1. **State the problem:** Solve the equation $$\log_2(6x + 1) + \log_2(4x - 2) = 7$$ for $x$.
2. **Recall the logarithm property:** The sum of logarithms with the same base can be combined as the logarithm of the product:
$$\log_b A + \log_b B = \log_b (A \times B)$$
3. **Apply the property:**
$$\log_2(6x + 1) + \log_2(4x - 2) = \log_2\big((6x + 1)(4x - 2)\big)$$
So the equation becomes:
$$\log_2\big((6x + 1)(4x - 2)\big) = 7$$
4. **Rewrite the logarithmic equation in exponential form:**
$$\log_2(y) = 7 \implies y = 2^7 = 128$$
Therefore:
$$(6x + 1)(4x - 2) = 128$$
5. **Expand the left side:**
$$6x \times 4x = 24x^2$$
$$6x \times (-2) = -12x$$
$$1 \times 4x = 4x$$
$$1 \times (-2) = -2$$
So:
$$24x^2 - 12x + 4x - 2 = 128$$
Simplify the middle terms:
$$24x^2 - 8x - 2 = 128$$
6. **Bring all terms to one side:**
$$24x^2 - 8x - 2 - 128 = 0$$
$$24x^2 - 8x - 130 = 0$$
7. **Simplify the quadratic equation by dividing all terms by 2:**
$$\cancel{2} \times 12x^2 - \cancel{2} \times 4x - \cancel{2} \times 65 = 0$$
$$12x^2 - 4x - 65 = 0$$
8. **Use the quadratic formula:**
$$x = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a}$$
where $a=12$, $b=-4$, $c=-65$.
Calculate the discriminant:
$$\Delta = (-4)^2 - 4 \times 12 \times (-65) = 16 + 3120 = 3136$$
Calculate the square root:
$$\sqrt{3136} = 56$$
9. **Find the roots:**
$$x = \frac{-(-4) \pm 56}{2 \times 12} = \frac{4 \pm 56}{24}$$
Two solutions:
$$x_1 = \frac{4 + 56}{24} = \frac{60}{24} = \frac{5}{2} = 2.5$$
$$x_2 = \frac{4 - 56}{24} = \frac{-52}{24} = -\frac{13}{6} \approx -2.1667$$
10. **Check domain restrictions:**
- Inside the logarithms, arguments must be positive:
$$6x + 1 > 0 \implies x > -\frac{1}{6}$$
$$4x - 2 > 0 \implies x > \frac{1}{2}$$
The stricter condition is $x > \frac{1}{2}$.
11. **Check solutions against domain:**
- $x_1 = 2.5$ satisfies $x > 0.5$.
- $x_2 \approx -2.1667$ does not satisfy $x > 0.5$.
Therefore, the only valid solution is:
$$\boxed{2.5}$$
Logarithmic Equation 4E07D8
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