$ n - \sqrt{n}$ $\Theta$ Complexity

Question

$ n - \sqrt{n} \leq n - \sqrt{n} + \sqrt{n}=n=O(n)$

But I don't know what I should do about $\Omega(.) , \Theta(.)$

Should I try to solve it with lim?

Answer 1

A hint: $\sqrt n \leq n/2$ for sufficiently large $n$.