I am a total beginner with the big O and big theta notation. How would I prove the following?
If $f(n) \in O(g(n))$, then $f(n)+g(n) \in \Theta (g(n))$.
I am not sure how to go from the definition of $f(n) \in O(g(n))$. What's confusing me is how to get to $(f+g)(n)$? Can someone please put me in the right direction?