Answer
Domain: $ (-\infty, 0) \cup (0,\infty) $
Range: $ (-\infty, 0) \cup (0,\infty) $
Work Step by Step
In a rational function, the denominator must not equal zero. So the function $ \frac{3}{x} $ is defined at all real numbers $x$ such that $ x\ne 0 $. This is also written as $ (-\infty, 0) \cup (0,\infty) $
The function $ \frac{3}{x} $ has a horizontal asymptote at $ y=0 $. So it's range is all real numbers $y$ such that $ y \ne 0 $ , also written as $ (-\infty, 0) \cup (0,\infty) $
