-0.73th root not working?

Question

I have a math assignment due tomorrow morning, nearly done however I've stumbleded upon a problem of mine. I'm normally using Wolfram Alpha for my calculations, which has worked for everything so far - besides this.

My problem is: $$\sqrt[-0,73]{\frac {17} {18}}.$$ I need to solve that, however if I put it into Wolfram Alpha, this will come: http://www.wolframalpha.com/input/?i=-0.73th+root+%2817%2F18%29 - It seems to work with all other numbers, but negative numbers in root. I tried solving this on my Texas Instrument calculator, but it put minus at the root instead of the the number before root (-0.73) - Then I tried making Excel do it, didn't work either.

Anything I'm missing? Thanks.

Answer 1

n^th root of a number a is defined as $a^\frac{1}{n}$

In your problem try writing $(\frac{17}{18})^\frac{1}{-0.73}$ which evaluates to $1.081446\ldots$ on WolframAlpha

http://www.wolframalpha.com/input/?i=%2817%2F18%29^%28-1%2F0.73%29

Answer 2

$\large\sqrt[n]{x^k}=x^{\Large\frac{k}{n}}$

Therefore: $\large\sqrt[-0.73]{\normalsize x^1}=\normalsize x^{\Large\frac{1}{-0.73}}=\Large\frac{1}{x^\frac{100}{73}}=\Large\frac{1}{\sqrt[73]{x^{100}}}$