Logarithmic equation evaluation

CAT 2023 Slot 2 · QA · Medium · Algebra

For some positive real number xx, if log3(x)+logx(25)logx(0.008)=163\log_{\sqrt{3}}(x) + \frac{\log_x(25)}{\log_x(0.008)} = \frac{16}{3}, then the value of log3(3x2)\log_3(3x^2) is

Answer

7

Explanation

First, simplify the terms: log3(x)=log31/2(x)=2log3(x)\log_{\sqrt{3}}(x) = \log_{3^{1/2}}(x) = 2 \log_3(x)

logx(25)logx(0.008)=log0.008(25)=log53(52)=23\frac{\log_x(25)}{\log_x(0.008)} = \log_{0.008}(25) = \log_{5^{-3}}(5^2) = -\frac{2}{3}

Substitute these into the equation: 2log3(x)23=1632 \log_3(x) - \frac{2}{3} = \frac{16}{3} 2log3(x)=6    log3(x)=32 \log_3(x) = 6 \implies \log_3(x) = 3

Now, evaluate log3(3x2)\log_3(3x^2): log3(3x2)=log3(3)+2log3(x)=1+2(3)=7\log_3(3x^2) = \log_3(3) + 2 \log_3(x) = 1 + 2(3) = 7

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