If I have an algorithm with the running time $T(n) = 5n^4/100000 + n^3/100$, I know that I get Θ$(n^4)$.
Now, if I have something like $T(n) = \frac{10n^2 + 20n^4 + 100n^3}{n^4}$, does this yield Θ$(n^3)$?
I am trying to eliminate low-order terms to use the Substitution method to prove this.
In your second example you have $T(n) = \Theta(1)$ as $n\to +\infty$.