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Discussion :: Square Root and Cube Root

  1. If x =\(\frac { \sqrt{3} +1} {\sqrt{3}-1 } \) and  Y = \(\frac { \sqrt{3} -1} {\sqrt{3}+1 } \) ,then the value of (x2 + y2) is:

  2. A.

    10

    B.

    13

    C.

    14

    D.

    15

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    Answer : Option C

    Explanation :

    X = \(\frac {( \sqrt{3} +1)} {(\sqrt{3}-1) } \) x \(\frac { (\sqrt{3} +1)} {(\sqrt{3}+1 )} \) = \(\frac { (\sqrt{3} +1)^2} {({3}-1 )} \) = \(\frac { 3+1+2\sqrt{3} } {2 } \) = 2+\( \sqrt{3}\)

     

    y =  \(\frac {( \sqrt{3} -1)} {(\sqrt{3}+1) } \) x \(\frac { (\sqrt{3} -1)} {(\sqrt{3}-1 )} \) = \(\frac { (\sqrt{3}-1)^2} {({3}-1 )} \)\(\frac { 3+1-2\sqrt{3} } {2 } \)= 2 -\( \sqrt{3}\)

     

     x2 + y2 = (2 +\( \sqrt{3}\) )2 + (2 - \( \sqrt{3}\))2

     

          = 2(4 + 3)

      

           = 14

     


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