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Find all real numbers x which satisty th...

Find all real numbers x which satisty the equation. `2log_2log_2x+log_(1/2)log_2(2sqrt2x)=1`

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To solve the equation \( 2 \log_2 (\log_2 x) + \log_{\frac{1}{2}} (\log_2 (2\sqrt{2}x)) = 1 \), we will proceed step by step. ### Step 1: Rewrite the logarithm First, we can rewrite the logarithm with base \( \frac{1}{2} \) in terms of base 2: \[ \log_{\frac{1}{2}} y = -\log_2 y \] Thus, the equation becomes: \[ 2 \log_2 (\log_2 x) - \log_2 (\log_2 (2\sqrt{2}x)) = 1 \] ### Step 2: Simplify the logarithm Next, simplify \( \log_2 (2\sqrt{2}x) \): \[ \log_2 (2\sqrt{2}x) = \log_2 (2) + \log_2 (\sqrt{2}) + \log_2 (x) = 1 + \frac{1}{2} + \log_2 (x) = \frac{3}{2} + \log_2 (x) \] Substituting this back into the equation gives: \[ 2 \log_2 (\log_2 x) - \log_2 \left( \frac{3}{2} + \log_2 x \right) = 1 \] ### Step 3: Isolate the logarithm Rearranging the equation: \[ 2 \log_2 (\log_2 x) = 1 + \log_2 \left( \frac{3}{2} + \log_2 x \right) \] Using properties of logarithms, we can express \( 2 \log_2 (\log_2 x) \) as: \[ \log_2 ((\log_2 x)^2) \] So we have: \[ \log_2 ((\log_2 x)^2) = 1 + \log_2 \left( \frac{3}{2} + \log_2 x \right) \] ### Step 4: Combine logarithms Using the property \( \log_a b + \log_a c = \log_a (bc) \): \[ \log_2 ((\log_2 x)^2) = \log_2 (2 \cdot \left( \frac{3}{2} + \log_2 x \right)) \] This implies: \[ (\log_2 x)^2 = 2 \left( \frac{3}{2} + \log_2 x \right) \] ### Step 5: Rearranging the equation Expanding and rearranging gives: \[ (\log_2 x)^2 - 2 \log_2 x - 3 = 0 \] ### Step 6: Solve the quadratic equation Let \( t = \log_2 x \). The equation becomes: \[ t^2 - 2t - 3 = 0 \] Factoring gives: \[ (t - 3)(t + 1) = 0 \] Thus, \( t = 3 \) or \( t = -1 \). ### Step 7: Find \( x \) Now, converting back to \( x \): 1. If \( t = 3 \): \[ \log_2 x = 3 \implies x = 2^3 = 8 \] 2. If \( t = -1 \): \[ \log_2 x = -1 \implies x = 2^{-1} = \frac{1}{2} \] ### Step 8: Check for validity Since \( \log_2 (\log_2 x) \) must be greater than 0, we check: - For \( x = 8 \): \( \log_2 8 = 3 \) (valid) - For \( x = \frac{1}{2} \): \( \log_2 \frac{1}{2} = -1 \) (not valid) ### Final Answer Thus, the only valid solution is: \[ \boxed{8} \]
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