Question

limit (x-->3)x^2-9/x-3=?

Answer 1

(x^2 - 9)
-----------
...x - 3

Factor the numerator to (x + 3)(x - 3)
(x + 3)(x - 3)
-----------------
.....(x - 3)

The x - 3 in the numerator cancels with the x - 3 in the denominator and you're left with
x + 3

Now, just substitute 3 into the equation
Lim (x - - > 3) x + 3 = 3 + 3
source: http://answers.yahoo.com/question/index?qid=20080430175035AA8GNh6