Derivatives

Thanks. I guess I had the right idea but felt like I was looking at a bunch of gibberish when I attempted it. It may have been the way I wrote it seeing as it suddenly looks much clearer than before. The only other thing troubling me so far would be fractions. I still have no clue what delta(x) cancels on the bottom of the formal definition when dealing with f(x) = x / (x - 1). This was an example in the book. Not sure if it's the denominator or the numerator but it just disappears in the book with no explanation as to how.