This is a function.
Work Step by Step
A function is a correspondence between a first set, called the domain, and a second set, called the range, such that EACH member of the domain corresponds to EXACTLY ONE member of the range. --- Keywords are emphasized. We see from the definition of the correspondence that EACH input from the domain has an arrow pointing from it to a value in the range. and only ONE arrow originates from each member of the domain. This is a function.