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Mathematics

Solve the following equation for x:

logx 1243=10\text{log}_x \space \dfrac{1}{243} = 10

Logarithms

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Answer

Given,

logx 1243=10logx 1logx 243=100logx (3)5=105logx 3=10logx 3=105logx 3=2x2=31x2=31x=3x=13.\Rightarrow \text{log}x \space \dfrac{1}{243} = 10 \\[1em] \Rightarrow \text{log}x \space 1 - \text{log}x \space 243 = 10 \\[1em] \Rightarrow 0 - \text{log}x \space (3)^5 = 10 \\[1em] \Rightarrow -5\text{log}x \space 3 = 10 \\[1em] \Rightarrow -\text{log}x \space 3 = \dfrac{10}{5} \\[1em] \Rightarrow \text{log}_x \space 3 = -2 \\[1em] \Rightarrow x^{-2} = 3 \\[1em] \Rightarrow \dfrac{1}{x^2} = 3 \\[1em] \Rightarrow \dfrac{1}{x} = \sqrt{3} \\[1em] \Rightarrow x = \dfrac{1}{\sqrt{3}}.

Hence, x = 13\dfrac{1}{\sqrt{3}}.

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