Solution
= Solution
Dividing by $n^2$ gives $10^5/n+2\to2$. Thus the quadratic term controls the growth:
$$
\boxed{10^5n+2n^2=\Theta(n^2),\quad\text{in particular }O(n^2).}
$$
The sharper <Big theta notation> also supplies the requested <Big O notation> bound.