Logarithmic Equation 2531C0
1. **State the problem:** Solve the equation $10\log(x-4) + 10\log(x-2) = \log 3^3$ using algebraic methods.
2. **Recall logarithm properties:**
- $a\log b = \log b^a$
- $\log a + \log b = \log(ab)$
- $\log 3^3 = \log 27$
3. **Apply properties:**
Rewrite the left side:
$$10\log(x-4) + 10\log(x-2) = \log((x-4)^{10}) + \log((x-2)^{10}) = \log\left((x-4)^{10}(x-2)^{10}\right)$$
4. **Combine logs:**
$$\log\left((x-4)^{10}(x-2)^{10}\right) = \log 27$$
5. **Set arguments equal:**
Since $\log A = \log B$ implies $A = B$, we have:
$$ (x-4)^{10}(x-2)^{10} = 27 $$
6. **Simplify:**
$$ \left[(x-4)(x-2)\right]^{10} = 27 $$
7. **Take 10th root:**
$$ (x-4)(x-2) = 27^{\frac{1}{10}} $$
8. **Expand product:**
$$ x^2 - 6x + 8 = 27^{\frac{1}{10}} $$
9. **Rewrite as quadratic:**
$$ x^2 - 6x + (8 - 27^{\frac{1}{10}}) = 0 $$
10. **Use quadratic formula:**
$$ x = \frac{6 \pm \sqrt{(-6)^2 - 4 \cdot 1 \cdot (8 - 27^{\frac{1}{10}})}}{2} = \frac{6 \pm \sqrt{36 - 32 + 4 \cdot 27^{\frac{1}{10}}}}{2} = \frac{6 \pm \sqrt{4 + 4 \cdot 27^{\frac{1}{10}}}}{2} $$
11. **Simplify under root:**
$$ \sqrt{4(1 + 27^{\frac{1}{10}})} = 2\sqrt{1 + 27^{\frac{1}{10}}} $$
12. **Final solutions:**
$$ x = 3 \pm \sqrt{1 + 27^{\frac{1}{10}}} $$
13. **Check domain:**
- $x-4 > 0 \Rightarrow x > 4$
- $x-2 > 0 \Rightarrow x > 2$
Only solutions with $x > 4$ are valid.
14. **Evaluate approximate values:**
Since $27^{1/10} \approx 1.38$,
$$ x = 3 \pm \sqrt{1 + 1.38} = 3 \pm \sqrt{2.38} $$
$$ \sqrt{2.38} \approx 1.54 $$
So,
- $x_1 = 3 + 1.54 = 4.54$ (valid)
- $x_2 = 3 - 1.54 = 1.46$ (invalid, domain restriction)
**Answer:**
$$ \boxed{x = 3 + \sqrt{1 + 27^{\frac{1}{10}}}} $$