Answer:
It is a relation and a function.
Explanation:
The expression:
is a relation because it connects x values of the Real number set with y values of the Real number set via this associated equation.
It is also a function,because this relation satisfies that for each x-value in the starting set called Domain (which in this case is as we said the Real number set), there is ONLY one value in the END set (called the Range) associated it.