Negative exponents work like this:
[tex]a^{-b}=\dfrac{1}{a^b}[/tex]
So, in order to evaluate a negative exponent, you simply have to invert the base, and then raise to the positive equivalent of the exponent.
As an example, here are the first three exercises:
[tex]8^{-3}=\dfrac{1}{8^3}=\dfrac{1}{512}[/tex]
[tex](-4)^{-5}=\dfrac{1}{(-4)^5}=-\dfrac{1}{1024}[/tex]
[tex]2k^{-4}=\dfrac{2}{k^4}[/tex]
You can work out the rest applying this logic.
