Answer
Domain: all real numbers
Range: $n(x) \leq 9$
Work Step by Step
The domain of $n(x)=9-x^4$ is all real numbers since the function is defined for all $x$.
For any value of $m(x)$ there is a corresponding value of $x$. However, when $x=0$, the maximum value of the function is 9, So the range is $n(x) \leq 9$.
