$\displaystyle -81^{-3/4}$

My steps:

$\displaystyle = 1 / (-81^3) ^ {1/4}$

$\displaystyle = 1 / (-531441) ^ {1/4}$

$\displaystyle = 1 / (something impossible)$

My book's answer:

$\displaystyle - 1/27$

Should my first step really be:

$\displaystyle - 1 / (81^3) ^ {1/4}$?