Your question is a little imprecise, but yes. As x gets infinitely large, k/x will ALWAYS approach zero.
In the case of f(x) = 17/x, it will still approach zero. 17/9999999999999999 is a very small positive number that's slightly above the x-axis.
In the case of f(x) = -17/x, it will also approach zero. The kicker is that -17/9999999999 is a very small NEGATIVE number that's slightly BELOW the x-axis.
Thus the first case, the graph approaches zero from above. One can say that lim x->inf (17/x) = 0+, where the + is tiny and almost a superscript. One can also say that lim x-->inf (-17/x) = 0-, where the - is a tiny superscript too.
However, don't say 17/inf = 0, or -17/inf = 0. It's an abuse of notation. Infinity's not a real number. Division by infinity isn't defined, since for division you need two numbers (and the second number CAN'T be zero!) Using the notation of limits is a much more accurate way to express these ideas.