What is the domain of this function. (Could someone explain it too? I wanna be able to do it myself as well)

[tex]answer \\ = - 2 , 2 ,3 , 4 \\ explanation \\ let \: r \: be \: a \: relation \: from \: a \: to \: b. \: then \: \\ the \: set \: of \: first \: components \: or \: the \\ set \: of \: elements \: of \: a \: are \: called \\ domain \: and \: the \: set \: of \: second \\ components \: or \: the \: set \: of \: elements \\ of \: b \: are \: called \: the \: range. \\ hope \: it \: helps[/tex]