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Posted by on Tuesday, October 25, 2011 at 1:38am.

In 11 years, the age of Russel will be half of the square of the age he was 13 years ago. Find his present age.

  • math - , Tuesday, October 25, 2011 at 3:12am

    x + 11 = ( 1 / 2 ) ( x - 13 ) ^ 2

    x + 11 = ( 1 / 2 ) ( x ^ 2 - 2 x *13 + 13 ^ 2 )

    x + 11 = ( 1 / 2 ) ( x ^ 2 - 26 x + 169 )

    1 / 2 ( x ^ 2 ) - 13 x - x + 169 / 2 - 11 = 0

    ( 1 / 2 ) x ^ 2 - 13 x - x + 169 / 2 - 22 / 2 = 0


    ( 1 / 2 ) x ^ 2 - 13 x - x + 147 / 2 = 0


    The exact solutions are:

    7

    or

    21

  • math - , Tuesday, October 25, 2011 at 3:15am

    In 11 years, the age of Russel will be half of the square of the age he was 13 YEARS AGO.

    For that reason present age = 21

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