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A complete study circle (UPSC / IAS / MBA / CAT)

a. Quantitative Ability

Find the value

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  • November 1, 2011 at 9:02 pm #2907
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    Keymaster

      Q. if a is positive and a^4 – 62a^2 +1 = 0 ; find a^3 +1/a^3
      424
      648
      392
      488

      November 1, 2011 at 9:04 pm #3022
      administration
      Keymaster

        a4– 62a2 + 1 = 0

        Dividing by a2 we get
        => a2 + 1/a2 = 62
        => (a + 1/a) = 8

        a3 + 1/a3 = (a + 1/a)(a2 – 1 + 1/a2) = 8x(62-1) = 488 Answer

         

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