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Mathematics

If ab=(ba)12x\sqrt{\dfrac{a}{b}} = \Big(\dfrac{b}{a}\Big)^{1 - 2x}, the value of x is :

  1. 34\dfrac{3}{4}

  2. 35\dfrac{3}{5}

  3. 34-\dfrac{3}{4}

  4. 35-\dfrac{3}{5}

Indices

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Answer

Given,

ab=(ba)12x(ab)12=(ba)12x(ab)12=(ab)(12x)(ab)12=(ab)(2x1)12=2x12x=1+122x=2+12x=32×2x=34.\Rightarrow \sqrt{\dfrac{a}{b}} = \Big(\dfrac{b}{a}\Big)^{1 - 2x} \\[1em] \Rightarrow \Big(\dfrac{a}{b}\Big)^{\dfrac{1}{2}} = \Big(\dfrac{b}{a}\Big)^{1 - 2x} \\[1em] \Rightarrow \Big(\dfrac{a}{b}\Big)^{\dfrac{1}{2}} = \Big(\dfrac{a}{b}\Big)^{-(1 - 2x)} \\[1em] \Rightarrow \Big(\dfrac{a}{b}\Big)^{\dfrac{1}{2}} = \Big(\dfrac{a}{b}\Big)^{(2x - 1)} \\[1em] \Rightarrow \dfrac{1}{2} = 2x - 1 \\[1em] \Rightarrow 2x = 1 + \dfrac{1}{2} \\[1em] \Rightarrow 2x = \dfrac{2 + 1}{2} \\[1em] \Rightarrow x = \dfrac{3}{2 \times 2} \\[1em] \Rightarrow x = \dfrac{3}{4}.

Hence, Option 1 is the correct option.

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