answer:
(a^-13) / (a^-6)
To rewrite this expression in the form of a to the power of n, we subtract the exponent of the denominator from the exponent of the numerator:
a^(-13 - (-6))
a^(-13 + 6)
a^-7
Therefore, the expression (a^-13) / (a^-6) can be rewritten as a^-7.