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Negative Fractional Exponent problem

  1. May 29, 2012 #1
    Hi All,

    Can anyone walk me through this problem. This is from an old med school entry test.

    The answer is 81 but I can't work out how the x terms cancel.



    3x(3x^ -1/3)^3

    Thanks in advance

    John
     
  2. jcsd
  3. May 29, 2012 #2
    [tex]\frac{3x}{(^3\sqrt{x})^3}3^3=\frac{3x}{x}3^3=27*3=81[/tex]

    Given of course that x is not 0.
     
  4. May 29, 2012 #3
    Hi Meldraft,

    It looks so simple I don't know why I didn't do it that way. Thanks very much.

    John
     
  5. May 29, 2012 #4
    It's very easy to put that 3^3 in the denominator by accident :wink:
     
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