1. The domain is all real numbers except x = 3, since at x = 3, the denominator becomes zero, and the function becomes undefined.
2. The range is all real numbers except y = 4, since the function can take any other real value.
3. The function is continuous and decreasing on the intervals (-∞, 3) and (3, ∞), so the interval of decrease is all real numbers except x = 3.
4. The horizontal asymptote is y = 0, since as x approaches positive or negative infinity, the function approaches zero.
5. The vertical asymptote is x = 3, since the denominator becomes zero at x = 3, and the function becomes undefined.
6. There is a hole in the graph at x = 3, since the function is undefined at this point. However, the hole can be "filled" by simplifying the function to (2x - 6)/(x - 3) and noting that the factor (x - 3) cancels out, leaving the function equal to 2 for all x not equal to 3.