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    What is the value of x=5+15−1x = \sqrt{\frac{\sqrt{5+1}}{\sqrt{5-1}}}x=5−1​5+1​​​ find the value of 5x2−5x−15x^2 - 5x -1 5x2−5x−1​​
    Question

    What is the value of x=5+151x = \sqrt{\frac{\sqrt{5+1}}{\sqrt{5-1}}} find the value of 5x25x15x^2 - 5x -1 ​​

    A.

    0

    B.

    1

    C.

    145314 - 5\sqrt3​​

    D.

    None of these

    Correct option is C

    Given:

    x=5+151x = \sqrt{\frac{\sqrt{5+1}}{\sqrt{5-1}}} 

    Solution: 

    5x25x15x^2 - 5x -1  

    x=5+151x = \sqrt{\frac{\sqrt{5+1}}{\sqrt{5-1}}} 

     x=5+151×5+15+1x = \sqrt{\frac{\sqrt{5+1}}{\sqrt{5-1}} \times \frac{\sqrt{5 + 1}}{\sqrt{5+1}}} 

    x = (5+1)251\sqrt{\frac{(\sqrt{5+1})^2}{\sqrt{5-1}}} 

     x=62 x=3x = \sqrt{\frac{6}{2}} \\\ \\x = \sqrt 3  

    Then the value of  5x25x15x^2 - 5x -1   = 5×35×315\times 3 - 5\times \sqrt3 -1   = 14 535\sqrt{3}

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