Are you sure that both a and b are zero?
I doubt it.
-8a^8b^-2/10a^-4b^-10
should surely be written as a fraction for clarity:
-8a^8b^-2
----------------- (at least this is how I interpret your question)
10a^-4b^-10
-8a^8 divided by 10a^(-4) comes out to (-8/10)a^12, and
b^(-2) divided by b^(-10) comes out to b^8
so that your final quotient is (-4/5)(a^12)(b^8).
