#### Answer

False

#### Work Step by Step

RECALL:
A function has every first component ($x$) paired with exactly one second component ($y$).
Note that in the given equation, almost all $x$ values are paired with 2 different y-values.
Example:
When x=2:
$y=\pm \sqrt{2^2-1}
\\y=\pm \sqrt{4-1}
\\y = \pm \sqrt{3}$
This means that the first component $x=2$, is paired with two second components: $y=\sqrt{3}$ and $y=-\sqrt{3}$.
Therefore, the given equation is not a function.