Item 1.
Consider all functions \(f: \{1,2,3,4,5\} \to \{1,2,3,4,5\}\text{.}\) How many functions are there all together? How many of those are injective? Remember, a function is an injection if every input goes to a different output.
Consider all functions \(f: \{1,2,3,4,5\} \to \{1,2,3,4,5\}\text{.}\) How many functions are there all together? How many of those are injective? Remember, a function is an injection if every input goes to a different output.