Question

d

Answer 1

For a relation to be a function, it can't have 2 or more of the same values in the domain. Do you know what to domain is?

Answer 2

actually every element of the domain can be assigned only one element. in this case
\[ \large 5\mapsto7\quad \text{and}\quad 5\mapsto8 \]
which is not possible. hence, the relation is not a function.