# 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