big-theta

Difference between lower bound and tight bound?

With the reference of this answer, what is Theta (tight bound)? Omega is lower bound, quite understood, the minimum time an algorithm may take. And we know Big-O is for upper bound, means the maximum time an algorithm may take. But I have no idea regarding the Theta. ...

What is the difference between Θ(n) and O(n)?

Sometimes I see Θ(n) with the strange Θ symbol with something in the middle of it, and sometimes just O(n). Is it just laziness of typing because nobody knows how to type this symbol, or does it mean something different? ...

Proving that a function f(n) belongs to a Big-Theta(g(n))

Its a exercise that ask to indicate the class Big-Theta(g(n)) the functions belongs to and to prove the assertion. In this case f(n) = (n^2+1)^10 By definition f(n) E Big-Theta(g(n)) <=> c1*g(n) < f(n) < c2*g(n), where c1 and c2 are two constants. I know that for this specific f(n) the Big-Theta is g(n^20) but I don't know who to prov...

Asymptotic runtime question

If f(n) is Θ(g(n)), then the function 2^(f(n)) is always Θ(2^(g(n))). Is this statement true or false, and why? ...