Consider the set of ordered pairs. Verify if it is one-to-one. If so, find its inverse.
$f=\left\{\right(2,9),(4,11),(6,15),(8,20\left)\right\}$

$f^{-1}={\(\left\[\lbrace\)(\(\frac\)19,\(\frac\)12),(\(\frac{1}{11}\),\(\frac\)14),(\(\frac{1}{15}\),\(\frac\)16),(\(\frac{1}{20}\),\(\frac\)18)\(\right\]\rbrace\)}$

$f^{-1}={\(\left\[\lbrace\)(\(\frac\)12,\(\frac\)19),(\(\frac\)14,\(\frac{1}{11}\)),(\(\frac\)16,\(\frac{1}{15}\)),(\(\frac\)18,\(\frac{1}{20}\))\(\right\]\rbrace\)}$

$f^{-1}={\(\left\[\lbrace\)(9,2),(11,4),(15,6),(20,8)\(\right\]\rbrace\)}$

The function is not one-to-one.