## Calculus with Applications (10th Edition)

$\boxed{\textbf{Not a function.}}$
A function is a rule that assigns to each element from one set exactly one element from another set. We can find an x to which more than one y will be assigned: If $x=8$, then y can be 2 or -2, for the relation to be valid. ( $8=2^{2}+4\quad$and$\quad 8=(-2)^{2}+4$) so this is not a function.