I have to prove two equations and I can't understand them. Any help would be grateful because I have to consign the whole project in two days.
These are the equations:
If $f(n)=O(g(n))$ and $z(n)=O(h(n))$, then $f(n)+z(n)=O(g(n)+h(n))$.
I have to prove that this is wrong: $f(n)=O(g(n)) \Rightarrow g(n)=O(f(n))$.
Thanks in advance.