Solve the following equation for \( x \). \( \log _{12}(x+4)+\log _{12}(x+5)=1 \) \( x=\square \)
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To solve the equation \( \log_{12}(x+4) + \log_{12}(x+5) = 1 \), we can use the property of logarithms that states \( \log_a(b) + \log_a(c) = \log_a(bc) \). First, combine the logs: \[ \log_{12}((x+4)(x+5)) = 1 \] Next, convert the logarithm to its exponential form: \[ (x+4)(x+5) = 12^1 \] This simplifies to: \[ (x+4)(x+5) = 12 \] Now, expand the left side: \[ x^2 + 5x + 4x + 20 = 12 \] Simplify: \[ x^2 + 9x + 20 = 12 \] Subtract 12 from both sides: \[ x^2 + 9x + 8 = 0 \] Now, factor the quadratic equation: \[ (x+8)(x+1) = 0 \] Setting each factor to zero gives: \[ x + 8 = 0 \quad \text{or} \quad x + 1 = 0 \] Thus, solving these yields: \[ x = -8 \quad \text{or} \quad x = -1 \] However, we need to check the validity of these solutions within the original logarithmic expressions. For \( x = -8 \): \[ \log_{12}(-4) \quad \text{(not valid)} \] For \( x = -1 \): \[ \log_{12}(3) \quad \text{(valid)} \] Hence, the only valid solution is: \[ x = -1 \] Thus, the final answer is: \( x = -1 \)
