Hi can you teach me how to prove the following Big-Oh, Big- Omega and Big-theta question step by step with explanation? Thank you.

5. * Select a theta notation for the function f(n) = 6n + 1. Choose one of the following answers. O O O O 0(1) Q(Ign) Qan) Q(nlgn) 6. * Select a big-o notation for the function f(n) = 3n2 + 2 nlgn Choose one of the following answers. 0(1) O(nlgn) O O(n) O O() 7. * Select a big-o notation for the function f(n) = 2 + 4 + 6 + ... + 2n Choose one of the following answers. O O(n) O O(nlgn) O O(n) O O(n)