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Mathematics

34+7\dfrac{3}{4 + \sqrt{7}} is equal to :

  1. 13(47)\dfrac{1}{3}(4 - \sqrt{7})

  2. 3(47)3(4 - \sqrt{7})

  3. 13(4+7)\dfrac{1}{3}(4 + \sqrt{7})

  4. 3(4+7)3(4 + \sqrt{7})

Rational Irrational Nos

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Answer

Rationalizing,

34+7×47473(47)(4)2(7)23(47)1673(47)913(47).\Rightarrow \dfrac{3}{4 + \sqrt{7}} \times \dfrac{4 - \sqrt{7}}{4 - \sqrt{7}} \\[1em] \Rightarrow \dfrac{3(4 - \sqrt{7})}{(4)^2 - (\sqrt{7})^2} \\[1em] \Rightarrow \dfrac{3(4 - \sqrt{7})}{16 - 7} \\[1em] \Rightarrow \dfrac{3(4 - \sqrt{7})}{9} \\[1em] \Rightarrow \dfrac{1}{3}(4 - \sqrt{7}).

Hence, Option 1 is the correct option.

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