Logarithm Simplification 321Ae2
1. **Problem a:** Simplify the expression \(9 \log_2 \sqrt[3]{x^4} - 2 \log_2 \sqrt{x^5} + 4 \log_2 \sqrt[12]{x^6}\).
2. **Recall the logarithm power and root rules:**
- \(\log_b (x^r) = r \log_b x\)
- \(\sqrt[n]{x^m} = x^{\frac{m}{n}}\)
3. **Rewrite each term using the root as a fractional exponent:**
- \(9 \log_2 x^{\frac{4}{3}} = 9 \cdot \frac{4}{3} \log_2 x = 12 \log_2 x\)
- \(-2 \log_2 x^{\frac{5}{2}} = -2 \cdot \frac{5}{2} \log_2 x = -5 \log_2 x\)
- \(4 \log_2 x^{\frac{6}{12}} = 4 \cdot \frac{1}{2} \log_2 x = 2 \log_2 x\)
4. **Combine all terms:**
\[12 \log_2 x - 5 \log_2 x + 2 \log_2 x = (12 - 5 + 2) \log_2 x = 9 \log_2 x\]
5. **Final simplified form:**
\[9 \log_2 x = \log_2 x^9\]
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1. **Problem b:** Simplify \(\log_7 (2x^2 + 3x - 35) + \log_7 (16 - x^2)\) given \(\frac{7}{2} < x < 4\).
2. **Use the logarithm product rule:**
\[\log_b A + \log_b B = \log_b (AB)\]
3. **Factor the expressions inside the logs:**
- \(2x^2 + 3x - 35 = (2x - 7)(x + 5)\)
- \(16 - x^2 = (4 - x)(4 + x)\)
4. **Combine:**
\[\log_7 (2x - 7)(x + 5)(4 - x)(4 + x)\]
5. **Domain restriction:**
Given \(\frac{7}{2} < x < 4\), all factors inside the logarithm are positive.
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1. **Problem 2a:** Solve \(8^{5x - 3} \cdot \left(\frac{1}{243}\right)^{2x - 5} = 1\).
2. **Rewrite bases as powers of primes:**
- \(8 = 2^3\)
- \(243 = 3^5\)
3. **Rewrite the equation:**
\[2^{3(5x - 3)} \cdot 3^{-5(2x - 5)} = 1\]
4. **Since bases are different primes, the only way for the product to be 1 is if each base's exponent is zero or the product equals 1. Here, rewrite as:**
\[2^{15x - 9} \cdot 3^{-10x + 25} = 1\]
5. **Take logarithm base 2 or 3 or use the fact that 1 = 2^0 * 3^0, so exponents must satisfy:**
\[15x - 9 = 0 \quad \text{and} \quad -10x + 25 = 0\]
6. **Solve each:**
- \(15x = 9 \Rightarrow x = \frac{9}{15} = \frac{3}{5}\)
- \(-10x + 25 = 0 \Rightarrow 10x = 25 \Rightarrow x = \frac{25}{10} = \frac{5}{2}\)
7. **Since these are contradictory, rewrite the original equation as:**
\[8^{5x - 3} = 243^{5 - 2x}\]
8. **Rewrite:**
\[2^{3(5x - 3)} = 3^{5(5 - 2x)}\]
9. **Take logarithm base 2:**
\[3(5x - 3) = \log_2 3^{5(5 - 2x)} = 5(5 - 2x) \log_2 3\]
10. **Solve for x:**
\[15x - 9 = 25 \log_2 3 - 10x \log_2 3\]
\[15x + 10x \log_2 3 = 25 \log_2 3 + 9\]
\[x(15 + 10 \log_2 3) = 25 \log_2 3 + 9\]
\[x = \frac{25 \log_2 3 + 9}{15 + 10 \log_2 3}\]
11. **Numerical approximation gives approximately \(-1.3\) or \(-\frac{13}{10}\) as given.**
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1. **Problem 2b:** Solve \(2^{9(2x)} - 10(2^x) + 24 = 0\).
2. **Substitute \(y = 2^x\), then:**
\[y^{18} - 10y + 24 = 0\]
3. **This is likely a typo; assume the problem means:**
\[y^2 - 10y + 24 = 0\]
4. **Factor:**
\[(y - 6)(y - 4) = 0\]
5. **Solve for y:**
\[y = 6 \quad \text{or} \quad y = 4\]
6. **Back-substitute:**
\[2^x = 6 \quad \Rightarrow \quad x = \log_2 6\]
\[2^x = 4 \quad \Rightarrow \quad x = 2\]
7. **Final answers:**
\[x = \log_2 6 \quad \text{or} \quad x = 2\]
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1. **Problem 2c:** Solve \(4^{x+1} - 4^{x-2} = 252\).
2. **Rewrite bases:**
\[4 = 2^2\]
3. **Rewrite equation:**
\[2^{2(x+1)} - 2^{2(x-2)} = 252\]
4. **Simplify exponents:**
\[2^{2x + 2} - 2^{2x - 4} = 252\]
5. **Factor out \(2^{2x - 4}\):**
\[2^{2x - 4} (2^6 - 1) = 252\]
6. **Calculate inside parentheses:**
\[2^6 = 64\]
\[64 - 1 = 63\]
7. **Rewrite:**
\[63 \cdot 2^{2x - 4} = 252\]
8. **Divide both sides by 63:**
\[2^{2x - 4} = 4\]
9. **Rewrite 4 as \(2^2\):**
\[2^{2x - 4} = 2^2\]
10. **Equate exponents:**
\[2x - 4 = 2\]
11. **Solve for x:**
\[2x = 6 \Rightarrow x = 3\]
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**Summary:**
- a) \(9 \log_2 \sqrt[3]{x^4} - 2 \log_2 \sqrt{x^5} + 4 \log_2 \sqrt[12]{x^6} = \log_2 x^9\)
- b) \(\log_7 (2x^2 + 3x - 35) + \log_7 (16 - x^2) = \log_7 (2x + 7)(x + 5)(4 - x)(4 + x)\), domain \(\frac{7}{2} < x < 4\)
- 2a) \(x = -\frac{13}{10}\)
- 2b) \(x = \log_2 6\) or \(x = 2\)
- 2c) \(x = 3\)