For this case we have that by definition of power properties it is fulfilled that:
[tex]a ^ {-1} = \frac {1} {a ^ 1} = \frac {1} {a}[/tex]
So, if we have the following expression:
[tex]-5x^{-4}[/tex]
We can rewrite it as:
[tex]\frac {-5} {x ^ 4} = - \frac {5} {x ^ 4}[/tex]
Answer:
[tex]- \frac {5} {x ^ 4}[/tex]