## Calculus with Applications (10th Edition)

$\boxed{\textbf{Is a function.}}$
A function is a rule that assigns to each element from one set exactly one element from another set. Written as $\sqrt{x}$, it is understood that we calculate the POSITIVE square root of the number x. For any non-negative x, there exists one and only one positive square root... so this rule is a function. (to each x-value, only one y-value is assigned)