Definition: We call a function μ: N⟶R negligible if for every positive polynomial p() there exists an N such that for all n > N, we have n(n) < 1/p(n).
e.g. functions 2^{-n^{1/2}} and n^{-log_2 n} are negligible.
Theorem: For any negligible function μ and any polynomial p, the function μ'(n)≝p(n)・μ(n) is also negligible
