\(\newcommand{\twoline}[2]{\begin{pmatrix}#1 \\ #2 \end{pmatrix}}\newcommand{\amp}{&}\)

The following functions all have domain [math]\{1,2,3,4\} and codomain [math]\{1,2,3,4,5\}\text{.} For each, determine whether it is (only) injective, (only) surjective, bijective, or neither injective nor surjective.

- [math]
f = \twoline{1 \amp 2 \amp 3 \amp 4}{1 \amp 2 \amp 5 \amp 4}\text{.} ? Injective Surjective Bijective Neither - [math]
f = \twoline{1 \amp 2 \amp 3 \amp 4}{1 \amp 2 \amp 3 \amp 2}\text{.} ? Injective Surjective Bijective Neither - [math]
f(x) gives the number of letters in the English word for the number [math]x\text{.} For example, [math]f(1) = 3 since “one” contains three letters.? Injective Surjective Bijective Neither