Solution (source code)

= Solution

Divide by the proposed comparison <function> $2^n$:
$$
\frac{n^2+n2^n}{2^n}=\frac{n^2}{2^n}+n\geq n.
$$
The ratio is unbounded, so no constant in the definition of <Big O notation> can work:
$$
\boxed{\text{False: }n^2+n2^n\ne O(2^n).}
$$