Example:Non-surjective

From CS2800 wiki

The following function is not surjective:

Fun-a1b23.svg

because there is no [math]x \href{/cs2800/wiki/index.php/%5Cin}{\in} \href{/cs2800/wiki/index.php/Enumerated_set}{\{a,b\}} [/math] with [math]f(x) = 3 [/math].