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Mathematics

Rationalise the denominator and simplify :

5+353\dfrac{\sqrt5 + \sqrt3}{\sqrt5 - \sqrt3}

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Answer

Since, the denominator = 53\sqrt5 - \sqrt3, its rationalizing factor = 5+3\sqrt5 + \sqrt3.

5+353=5+353×5+35+3=(5+3)2(5)2(3)2=5+3+21553=8+2152=4+15\dfrac{\sqrt5 + \sqrt3}{\sqrt5 - \sqrt3} = \dfrac{\sqrt5 + \sqrt3}{\sqrt5 - \sqrt3} \times \dfrac{\sqrt5 + \sqrt3}{\sqrt5 + \sqrt3}\\[1em] = \dfrac{(\sqrt5 + \sqrt3)^2}{(\sqrt5)^2 - (\sqrt3)^2} \\[1em] = \dfrac{5 + 3 + 2\sqrt{15}}{5 - 3} \\[1em] = \dfrac{8 + 2\sqrt{15}}{2}\\[1em] = 4 + \sqrt{15}

Hence, 5+353=4+15\dfrac{\sqrt5 + \sqrt3}{\sqrt5 - \sqrt3} = 4 + \sqrt{15}.

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