Question bank/JEE Main/Mathematics

JEE MainMathematicsEasyLogarithm and its applications

The value of
1log⁡bc(abc)+1log⁡caabc+1log⁡ab(abc)\frac{1}{\log_{\sqrt{bc}}(abc)} + \frac{1}{\log_{\sqrt{ca}}abc} + \frac{1}{\log_{\sqrt{ab}}(abc)}
is equal to

Show answer and solution
1log⁡bC(abc)+1log⁡caabc +1log⁡ab(abc)\frac{1}{\log_{\sqrt{bC}}(abc)} + \frac{1}{\log_{\sqrt{ca}}{abc}\ } + \frac{1}{\log_{\sqrt{ab}}{(abc)}}
=log⁡abcbc+log⁡abcca+log⁡abcab= \log_{abc}\sqrt{bc} + \log_{abc}\sqrt{ca} + \log_{abc}\sqrt{ab}
=12(log⁡abcbc+log⁡abcca+log⁡abcab)= \frac{1}{2}\left( \log_{abc}bc + \log_{abc}ca + \log_{abc}ab \right)
=12(log⁡abc(bc×ca×ab))= \frac{1}{2}\left( \log_{abc}(bc \times ca \times ab) \right)
=12(log⁡abc(abc)2)= \frac{1}{2}\left( \log_{abc}(abc)^{2} \right)
=12×2log⁡abcabc= \frac{1}{2} \times 2\log_{abc}abc
= 1

Source: Grass-G / M-05 Mathematics Paper 10 October.docx

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