Answer
$9x^{-8}y^{4} =\dfrac{9y^4}{x^8}$
Work Step by Step
RECALL:
The negative-exponent rule of exponents states that:
$a^{-m} =\dfrac{1}{a^m}$ and $\dfrac{1}{a^{-m}} = a^m$, where $a \ne 0$.
Use the negative-exponent rule to find:
$9x^{-8}y^{4} = 9 \cdot \dfrac{1}{x^8} \cdot y^4 =\dfrac{9y^4}{x^8}$