Answer
$\displaystyle -\frac{1}{27}$
Work Step by Step
We simplify:
$-81^{-3/4}=(-\displaystyle \frac{1}{81})^{3/4}=-(\sqrt[4]{\frac{1}{81}})^3=-(\frac{1}{3})^3 =-\frac{1}{27}$
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