Attempt $1$:$3$ attempts remaining.

Let $f(x)$ be defined as follows.

$f(x)=\frac{x^2-9}{x^2-8x15}$

Give the interval$($s$)$ on which the function is continuous. Use interval notation, or enter DNE if no such intervals exist. Include the union symbol when entering multiple intervals.

Interval$($s$)$ of continuity: $$