1- c cannot be 0 or negative, so you can assume that.
2. Growth is log(n)lower than growth nfor each n > 1, for example. Since Ω (n) is a set of functions that “grow more” than a function f(n) = n, log (n) is not Ω (n). But you could say n = Ω (log (n)), although that would not be an asymptotic dense estimate.
3- , , n0. - n0 , . (log (n) = Ω (n)) , n >= n0. , log (n) n .