coercive

Concept for function

continue function $f$ on unbounded(def of bounded) set $S\subseteq {\mathbb{R}}^n$ is coercive if

$$\underset{||x||\to \infty }{\lim }f(x)=+\infty$$

Example

$x^4-3x^3+2x+3$ is coercive.
but $x^3+2x^2-x+5$ is not coercive.