Little-O Estimate for Real Function/Examples/x is Little-O of x^2 at Infinity

Example of Little-$\oo$ Estimate for Real Function
Let $f: \R \to \R$ be the real function defined as:
 * $\forall x \in \R: \map f x = x$

Then:
 * $\map f x = \map \oo {x^2}$

as $x \to \infty$.

Proof
Let us consider the real function $g: \R \to \R$ defined as:
 * $\forall x \in \R: \map g x = x^2$

Then we have that:

Hence the result.