Phenomenology, Logic and the Philosophy of Mathematics
Richard Tieszen
ISBN 0521837820
Essay #3
Varieties of Constructive Mathematics
Douglas S. Bridges, Fred Richman
ISBN 0521318025
Lecture Note #79
How to Read and Do Proofs: An Introduction to Mathematical Thought Processes
Danial Solow
ISBN: 0471680583
Page 179
Just three I have sitting on my shelf.
You are correct on your notation, however, you are incorrect as to your interpretation OF ZERO. Zero is a non-number, it is a placeholder. While your interpretation would be valid if we were approaching the asymptote at any real number, it is incorrect when we are dealing with Zero.
Zero is like infinity in that it is very difficult to play with accurately. It has its own set of rules and regulations. Now, most of those can be totally ignored when you’re doing something as generic as building a skyscraper, launching a rocket, etc. However, in pure, theoretical, mathematics - the language of the universe, IMHO - those rules do bear an impact.
Remember, rules had to be invented to allow you to find real solutions for answers containing the square root of -1, same with division by zero, same with handling answers where literally, the answer is both negative infinity and positive infinity.
In my, overly simplified, example, you determine which polarity of infinity you are approaching by determining which polarity of zero you are dividing by. That will tell you from which direction you approach infinity/negative infinity.
Yes, an instructor would probably tell you with a superscript + or -; but in real mathematics you do not have a professor to just tell you if you approach from the left or the right, you have to determine that yourself. You can most easily determine that by determining if zero is positive or negative. (did you add to get to zero, then it is negative; did you subtract to get to zero, then it is positive.)