Thread: Help~~about the theta notation

the question is
find a theta notation for each expression
2+4+8+...+2^n

My sol:
because 2+4+8+...+2^n<=2^n+2^n+...+2^n+2^n
so O(2+4+8+...+2^n)=O(n)
is that correct???
what is omega???
and theta???

its

Read Big O notation - Wikipedia, the free encyclopedia