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Mathematics

If ab=23÷(23)0;then(ab)2\dfrac{a}{b} = \dfrac{2}{3} ÷ \Big(-\dfrac{2}{3}\Big)^0; \text{then} \Big(\dfrac{a}{b}\Big)^{-2} is equal to:

  1. 49\dfrac{4}{9}

  2. 49-\dfrac{4}{9}

  3. 94\dfrac{9}{4}

  4. 94-\dfrac{9}{4}

Indices

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Answer

Given, ab=23÷(23)0\dfrac{a}{b} = \dfrac{2}{3} ÷ \Big(-\dfrac{2}{3}\Big)^0

As we know that a0 = 1

ab=23÷1ab=23(ab)2=(23)2(ab)2=(32)2(ab)2=94.\Rightarrow \dfrac{a}{b} = \dfrac{2}{3} ÷ 1 \\[1em] \Rightarrow \dfrac{a}{b} = \dfrac{2}{3}\\[1em] \Rightarrow \Big(\dfrac{a}{b}\Big)^{-2} = \Big(\dfrac{2}{3}\Big)^{-2}\\[1em] \Rightarrow \Big(\dfrac{a}{b}\Big)^{-2} = \Big(\dfrac{3}{2}\Big)^2 \\[1em] \Rightarrow \Big(\dfrac{a}{b}\Big)^{-2} = \dfrac{9}{4}.

Hence, option 3 is the correct option.

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