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JEE MainMathematicsEasyLogarithm and its applications

If log⁡a(ab)=x\log_{a}(ab) = x then log⁡b(ab)\log_{b}(ab) is equal to

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log⁡a(ab)=x\log_{a}(ab) = x
log⁡aa+log⁡ab=x\log_{a}a + \log_{a}b = x
log⁡ab=x−1\log_{a}b = x - 1
log⁡ba=1x−1\log_{b}a = \frac{1}{x - 1}
log⁡ba+log⁡bb=1x−1+1\log_{b}a + \log_{b}b = \frac{1}{x - 1} + 1
⇒log⁡b(ab)=1xx−1\Rightarrow \log_{b}(ab) = \frac{1x}{x - 1}

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

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