## Calculus (3rd Edition)

$f(x)=x^2+2$ is not one-to-one, $f(x)=x^2+2$ is one-to-one on $[0,\infty)$.
$f(x)=x^2+2$ is not one-to-one, because, for example $f(-1)=f(1)$ and $-1\neq 1$. $f(x)=x^2+2$ is one-to-one on $[0,\infty)$ (the right side of the parabola).