# time complexity – Prove a lower bound

Prove: $$n^{5}-3n^{4}+logleft(n^{10}right)∈ Ωleft(n^{5}right)$$.

I always get stuck in these types of questions, where there is a $$”-(xy^{z})”$$ in the expression.
Whenever I see the solutions for these type of questions, I can’t identify a single method that works every time and it’s frustrating. How do I approach these types of questions?