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Mathematics

If log xlog 5=log y2log 2=log 9log13\dfrac{\text{log x}}{\text{log 5}} = \dfrac{\text{log y}^2}{\text{log 2}} = \dfrac{\text{log 9}}{\text{log}\dfrac{1}{3}}, find x and y.

Logarithms

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Answer

Given,

log xlog 5=log y2log 2=log 9log13\dfrac{\text{log x}}{\text{log 5}} = \dfrac{\text{log y}^2}{\text{log 2}} = \dfrac{\text{log 9}}{\text{log}\dfrac{1}{3}}

Considering,

log xlog 5=log 9log13log x=log 9 × log 5log13log x=log 9 × log 5log 1 - log 3log x=log 32×log 50 - log 3log x=2log 3 × log 5-log 3log x=-2log 5log x=log 52x=52=125.\Rightarrow \dfrac{\text{log x}}{\text{log 5}} = \dfrac{\text{log 9}}{\text{log}\dfrac{1}{3}} \\[1em] \Rightarrow \text{log x} = \dfrac{\text{log 9 × log 5}}{\text{log}\dfrac{1}{3}} \\[1em] \Rightarrow \text{log x} = \dfrac{\text{log 9 × log 5}}{\text{log 1 - log 3}} \\[1em] \Rightarrow \text{log x} = \dfrac{\text{log 3}^2 × \text{log } 5}{\text{0 - log 3}} \\[1em] \Rightarrow \text{log x} = \dfrac{\text{2log 3 × log 5}}{\text{-log 3}} \\[1em] \Rightarrow \text{log x} = \text{-2log 5} \\[1em] \Rightarrow \text{log x} = \text{log 5}^{-2} \\[1em] \Rightarrow x = 5^{-2} = \dfrac{1}{25}.

Considering,

log y2log 2=log 9log13log y2=log 9×log 2log 1 - log 3log y2=log 32×log 20 - log 3log y2=2log 3×log 2-log 3log y2=-2log 2log y2=log 22y2=22y=122=12.\Rightarrow \dfrac{\text{log y}^2}{\text{log 2}} = \dfrac{\text{log 9}}{\text{log}\dfrac{1}{3}} \\[1em] \Rightarrow \text{log y}^2 = \dfrac{\text{log 9} \times \text{log 2}}{\text{log 1 - log 3}} \\[1em] \Rightarrow \text{log y}^2 = \dfrac{\text{log 3}^2 \times \text{log 2}}{\text{0 - log 3}} \\[1em] \Rightarrow \text{log y}^2 = \dfrac{\text{2log 3} \times \text{log 2}}{\text{-log 3}} \\[1em] \Rightarrow \text{log y}^2 = \text{-2log 2} \\[1em] \Rightarrow \text{log y}^2 = \text{log 2}^{-2} \\[1em] \Rightarrow y^2 = 2^{-2} \\[1em] \Rightarrow y = \sqrt{\dfrac{1}{2^2}} = \dfrac{1}{2}.

Hence, x=125and y=12.x = \dfrac{1}{25} \text{and y} = \dfrac{1}{2}.

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