Negative Fractional Exponent problem

1. May 29, 2012

jdoyle

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

John

2. May 29, 2012

meldraft

$$\frac{3x}{(^3\sqrt{x})^3}3^3=\frac{3x}{x}3^3=27*3=81$$

Given of course that x is not 0.

3. May 29, 2012

jdoyle

Hi Meldraft,

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

John

4. May 29, 2012

meldraft

It's very easy to put that 3^3 in the denominator by accident