Determine whether $F(x)= 5x+10$ is $O(x^2)$ Please, can someone here help me to understand the Big-O notation in discrete mathematics?

Determine whether $F(x)= 5x+10$ is $O(x^2)$


It is as $x \to \infty$.
Actually, $5x+10 = o(x^2)$ as $x \to \infty$
(little-oh)
since $\lim_{x \to \infty} \frac{5x+10}{x^2} = 0$.
However,
$5x+10 \ne O(x^2)$ as $x \to 0$,
and  $5x \ne O(x^2)$ as $x \to 0$,
because
there is no real $c$ such that
$5x < c x^2$ as $x \to 0$.
Since $x \to 0$ and $x \to \infty$ are the two common
limits for big-oh notation,
it is important to state which one is meant.
